I haven't been with Trek America but I did travel around the US for two and a half months last year with my boyfriend. I do get emails from Trek America for some reason (I must have signed up for them at some point but I don't remember doing it!) and have noticed that they seem quite expensive compared to just organising everything yourself, especially considering most of the tours don't include accommodation, food etc. Our whole trip, including accommodation, food, tickets for various attractions and travel expenses cost just over £4000, and we visited most of the main cities on the West and East coast of the USA (Los Angeles, Las Vegas, Santa Barbara, San Francisco, Boston, New York, Philadelphia, Atlantic City, Washington DC, Orlando, Miami). We stayed in private rooms in hostels/motels, but ate cheaply and didn't drink over there, but had the time of our lives and would recommend it to anyone.
Obviously, it all depends on where you want to travel to, how long you want to go for, what your budget is, whether you plan on going out at night over there etc, but I don't know if it is worth the cost of going with a tour group, when essentially they are just providing a guide and transport from place to place, which you can get extremely cheap over there anyway with companies like Megabus and Greyhound.