2 to 3 months road trip

Agree with others--a sedan in the Toyota Corolla class would be fine. A somewhat larger car or a small SUV (Toyota RAV4 or similar) will give you more space. Your itinerary is a bit generic and misses some worthwhile places.

I guess I'm seeing a revised itineary--no Florida or Texas but places you could drop or reroute. Unless you like old house architecture al lot, I'd skip Savannah as its rather similar to Charleston but without the great restaurants, ocean access, etc. Going across southern Georgia and Alabama will be boring. Okefeneokee swamp and the barrier islands like Cumberland would be better uses of time. Chicago to the Smokies is a boring drive and frankly you'd be better off seeing less visited areas of the Appalachians in West Virginia in conjunction with DC. San Diego is nice but skippable. The traffic between there and LA is always heavy and the major routes are boring. You can hear the blues in Chicago--you don't need Memphis unless you really want the kitsch of Elvis' house.

Like others, I think you need objectives rather than a bucket list. National parks are not always the most notable places and many past their prime places are heavily marketed toward foreign tourists--so places that turn up on top 10 lists of whetever often aren't worth the effort.

August is heavy tourism time. Doing the bulk of your trip in Sept/Oct will get you the best weather and relatively few people at major attractions away from big cities. November means shorter days, with daylight ending before 1800 in many places.

1. You plan to go straight through from Denver to Conway, Arkansas? Since all Germans are presumed to have Karl Mai Syndrome, why don't you check out the numerous places that have Old West connections? The Little Bighorn is where Lieutenant Colonel (not general!) Custer met his fate on what is now the Custer Battleground in Montana. Wyoming, Nebraska, and Kansas are full of sites related to the covered wagon days of the Pony Express, railroad building, Oregon and Santa Fe Trails. Colorado has Bent's Old Fort, a tradilng post reconstruction on the original site along thke Santa Fe Trail. If you want to see what the west looked like, right down to skinning buffalo, this is the place. The Washita Battlefield in the far west of Oklahoma is another Custer site. The Sand Creek Massacre site in eastern Colorado is also part of the story. Missouri is where thousands of German '48ers wound up, and they were steadfast for the Union. They had been run out of ht Old Country,and they did not want to be run out of the new country, or to have the worst of the old country, slavery, dominant in their new home. The Missouri state capitol buildng in Springfield has an excellent presentation on Missouri in the Civil War, and the contributions of the Germans. Those Turnvereins converted very quickly into regiments. I nominate Missouri as the most Euroupean state, because it has been through occupation and the brutality of back and forth civil war. Suggestion: slow down and smell the historical roses

2. You mention a Comfort Inn. That chain, which includes Rodeway, Quality and others, has an incentive plan that can produce free nights after 2-4 stays. Some plans are tied into a credit card. You should definitely check it out. Other chains, such as Days Inn , Motel Six, and Holiday Inn Express also have incentive plans. You don't have to pay full price all the time.

3. Great that you do intend road time, that is the way to see the USA. Simply flying in and flying out makes it like a visit to a string of islands.

4. Gute Reise!

Personally I think a strategy where you visit a "string of islands" is a far better way to experience the highlights of the Lower 48 states of the US.

The highlights are superb, but there are hundreds of miles of country and landscape that even the most charitable traveller would concede is rather boring, even if there is a famous bluegrass banjo museum, or a memorial to the man who invented the disposal diaper ... or whatever. It's simply not worth it.

I would look at a Northeast circuit, then a flying visit to either Chicago or New Orleans, or both, then spend the bulk of your time in the eleven western-most states.

A much better use of your time than driving across the whole place - especially up down leftwards rightwards sideways and much else. The country west of I-25 is definitely the best, and why you should bother visiting at all.

If they want a road trip, they should take a road trip---they have the time for it. I periodically have to decide between flying and driving a trip of 400 miles---you;'d think it would be an easy choice with a flight of about an hour. With delays, security, etc. the flight sometimes has taken longer than the drive. The drive has some scenic stretches and places to stop (excellent pies, the odd memorial including one related to 9-11), but parts are tedious, congested or boring. Price is the first consideration, sometimes weather. But my point is that flying has fewer intrinsic advantages in the context of a long trip (and sometimes for a short one) and there are plenty of non-bucket list/stereotyped places to see between Boston & Chicago. Yes there are "classic" road trips like Route 66 which is a just an overhyped nothing marketed to foreigners--kind of like stringing together junk like the blarney stone on a featureless landscape, but there are ways to see the center of the country or the Southwest that are much more interesting.

That's all perfectly reasonable, and we too have to toss up about flying or driving 700 km (400 miles). But that wasn't my main point. I was just pushing back against the suggestion above that you have to drive through days of cornfields and a large number of nondescript cities in order to see the Real America.

I think the "island" approach is both reasonable and realistic, and made better if they have 2-3 months.

The poster is a German who has indicated that he and his companion are fortunate to have the time and motivation to make an more intensive examination of the country, rather than the more common and time-driven point to point excursions, punching the beaten path points along the way. Perhaps I project my own inclinations on to others, but I certainly enjoyed crossing Russia on the Trans Siberian, Australia on the Ghan, across the US by rail and road, the Alaska Highway more than once, road across the Kalahari from Botswana to Windhoek, and rail across Panama (the first transcontinental railroad, by the way).

As is frequently noted on these pages, the US does not have the type of public transportation available in more compact countries. The roads and motels are built to accommodate motor vehicles, and this is how most Americans see their country. I agree that once one has driven across Texas in a dry season, you don't learn much by doing it again. However, i do feel that a cross country drive is worthwhile. Yes, it can also be a test of the strength of relationships, but so can the Trans Siberian, or even a daily car pool!

The poster is a German who has indicated that he and his companion are fortunate to have the time and motivation to make an more intensive examination of the country, rather than the more common and time-driven point to point excursions, punching the beaten path points along the way.

But it isn't an either / or choice ... you can have long, scenic, and rewarding road-trips in the US, and see a great deal, but never be underwhelmed or bored - LA > Seattle > Glacier NP > Yellowstone NP > GCNP > Las Vegas ... for example. But driving across largely flat agricultural states dotted with fairly uninteresting population centres, is not often the way to see the best.

There are a lot of wonderful sites / sights in Australia too of course, but they are not often best seen by driving for days between them. Same applies to the US ... it might be of intrinsic interest to its residents, but hardly the stuff of memorable international holidays.

And speaking from experience, 8-12 weeks is not a long time on the road ... so you might as well cut out the dull, and focus on the beautiful.

I guess I'm seeing a revised itineary

Same here.

In that vein:
I think you are not organizing your route properly. Regardless of how much you enjoy cornfields, you spend a lot of hours on the road needlessly after Colorado. Instead of heading through Arkansas (why???), head straight east to Chicago, then you can follow the river south. It'll look more like this (roughly, I left a lot of locations out as I only wanted to provide the basic outline).

They're using an app to plan the trip and they started with typical "list of" places. They need to figure out what they actually want to see.

If you are headed to the UP, I recommend a day at Mackinaw City to enjoy the amazing day and night views of the Mackinac Bridge. Mackinac City also boasts the fort and the city itself for Mackinac Island Ice Cream and great eats. Be sure to the book the extended ferry ride that takes you under the bridge for unbelievable shots of the bridge. The Island has affordable hotels but be sure to book early as they book quickly June-September. As you probably know, the island doesn't allow vehicles so you can arrange ahead of time for a horse drawn taxi to take you and your luggage to your hotel. You can also rent a horse or bike to get around the island!

https://www.travel-mi.com/mackinac-island.html