taking mezcal home to the US??

Should be no problem into USA. Declare it on the customs form. 1 bottle liquor.
We took in four bottles of tequila each last trip, and into Mormon Salt Lake!
warning the new bottles of Gran Centenario Reposado have a plastic pourer top which can leak in your luggage.

The security rules limiting the amount of liquids pertains to carry on only. But be aware different states have rules about how much you can bring back. I'm quite sure they all allow at least a quart. But some do not allow more than that.

The customs requirements in the USA pertain to what you bring back, in your luggage . . . or carry-on, if I'm remembering correctly. Packing glass bottles in checked luggage that have seals that may not be tight enough given pressure changes may not be a wise thing to do (because of the possibility of leaking). If your luggage is inspected before take-off the bottle may be removed if the inspectors feel it's not secure enough (or if they're thirsty!). Though it's usually a little more expensive buying it this way - you can purchase Mezcal in the duty free shop and carry it on the plane with you.

Can't vouch for mezcal, but rum bottles travels very well in checked-in luggage.. Have hauled 20 bottles or more without a mishap.. I roll bottle up in pair of jeans (anything) and pack in center of bag.. bottles have never leaked..

2 - 950 ml. bottles are the legal limit.. any more and they will charge you a tax..

I had no problem bringing mescal back in my checked luggage two years ago -- and I claimed it on my customs form as mescal. One thing I did do was buy smaller bottles of it because the smaller bottles are less prone to breaking (according to my engineering science friend).

Last Friday leaving France we were allowed to bring duty freee bottles on the plane. On arrival in Atlanta to make a connecting flight we were advised all bottles had to be in checked luggage and could not be carried on. A co-wroker coming back from Mexico yesterday had the same experience. So it appears for the moment- no booze in carry- on, checking it through is fine. It is kind of a scam as on departure in another country you can and are encouraged to buy and carry it on, but not in the U.S. I had one small soft luggage that a bottle would have been broken in, so I just gave my wine to a Delta lady in Atlanta- she was most happy. My co-worker said the same of the return from Cancun via Detroit. A lot of people with connections were just dumping the bottles they had carried on as they had no room in checked luggae.

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<hr>So it appears for the moment- no booze in carry- on<hr></blockquote>
For people flying into their home city from Mexico, and not flying onward . . . carry-on works fine. For those people needing to connect to another flight (many) the additional challenge of carrying on any liquids when boarding those onward flights, as you indicate, may be insurmountable. Not all carry-on is inspected (when you're already within a secure zone), however. For many people it'll be best to leave the liquor in Mexico.