Is there an equivalent bike to the Thorn Nomad available in the United States?
I suppose it depends on what you mean by 'equivalent'. If you mean, a 26' touring bike designed for all types of road (and no road) conditions, there are quite a few I think. There is a fairly comprehensive list of American touring bike manufacturers here.
I'd suggest looking at the Surly Long Haul Trucker or the Gunnar Rock Tour - not fully equivalent, but aimed at the same sort of market (the latter is a bit more of an MTB in design). Kona (not on the Adventure Cycling Association list) are also now doing some fairly hard core touring bikes.
If you are interested in 700cc wheels, then i think lots of cyclocross bikes would make a pretty good equivalent, so long as they have rack and mudguard (fender) eyelets.
BTW, I've just seen that Thorn are doing a clearout of Nomads - selling them off at £999. Looks good value for me if you are in the sterling zone.

Sorry, yes I mean "a 26" touring bike designed for all types of road (and no road) conditions." I'm in the middle of planning an around the world trip; I've got a LHT w/ 700c wheels but have been thinking of going with a 26" tourer. Just trying to decide if it's worth switching over and seeing what my options are on the US side of the pond.

I can't think of any American manufacturers that make a bike quite as ugly as a Thorn. It must have taken Thorn years of R & D to get their bikes looking the way they do.
What about a Koga Miyata World Traveller, or perhaps a Rivendell Atlantis, or Bruce Gordon (though he's a bit of a grumpy prick if you believe other's feedback).
Hard to think of a more suitable bike for a RTW tour than a well specced LHT. They do 26" versions according to the website, but I think thats for the smaller sizes only.
I think most custom builders would make a frame suitable for 26" wheels, but if its touring geometry then it'll always look a little odd - any 26' tourer will look a bit ugly. Personally i wouldn't care, good looking bikes are for crusing your locality, for a RTW you want practicality all the way though.
If you want something more mtb like than a classic tourer, then the Gunnar Rock Tour is definitely worth a look, its a very handsome looking bike and it would allow you to do trail riding when you are tired hauling your kit.

There's nothing particularly amazing about a Thorn beyond its breathtaking ugliness. If you want something like it any framebuilder would be able to sort you out, or you could look at some of the options above.

Very nice. Thanks for the suggestions. I'll do more research, but proabaly stick with the LHT; I've got it dialed in. But you know, I keep looking at online journals and very few people go with 700c on around the world trips. I guess it's that same ol' 26" vs. 700c debate I've been struggling with that's been hashed out over and over. I will have a spare folding and spare tubes (plus patch kit) and can always have something shipped if need be.

Oh, and never really thought of the Thorn Nomad as an ugly bike, but I am an ugly American so my judgement is a little off. ;-)
Well, i kinda like the Nomad too - its not elegant, but I've always thought it has a certain ungainly attitude that sets it apart, a Hilary Swank of bikes among a sea of Gwyneth Paltrows.
Hmm... now what was my point? Oh yes, I was going to say that although I've never heard of it done before, I don't see any reason why a good local welder couldn't convert your LHT to 26" wheels, if thats your preference. I'd assume its only a matter of changing the forks and welding in new eyelets for the brakes. I don't know for certain if it would work, but it would certainly be a lot cheaper than a new bike or frame.