Forgive me for my ignorance, but isn't AMSA really,
really liberal, as in holding hands under trees and having vigils liberal? (
http://www.amsa.org/humed/COH.cfm)
Amazingly, at the club fair last year, the representatives for AMSA and TMA were both unable to tell me what their organizations actually stood for. My advice:
check them out before the club fair so that you know when you're standing at the table what they stand for and what they are good for. For goodness sake don't get a credit card just for the promise of a book. You can get books in other ways; you can get other incentives if you really need another credit card; make an intentional political statement if you like, but you don't want to make an accidental political statement.
AMSA:
From what I learned online: yes, if you don't want your money being used by an organization to promote a government-run single-payer health care system, don't sign up for AMSA. It's the first thing on their
priority list, and their other major things are essentially pretty-sounding talk.
For those whose political buttons get pushed by this sort of stuff, sure, you can spend your money if you like, but I'm still skeptical. It doesn't seem to be an organization with any impact. Who really listens to a bunch of students wax earnest on topics such as "global health equity" and "enriching medicine through diversity"? It's probably a self-licking ice-cream-cone in terms of actual impact on the world. You'll do more good in the world if you give that same money to a worthwhile charity instead. (Or use it to buy yourself & your friends drinks after tests. You'll all need them.)
TMA:
Tort reform in Texas seems to have made Texas one of the friendlier places to practice.
TMA claims to have taken a large part in that fight. The issues on their "
hot topics" page involve more definite action than the vague "issues" on the AMSA web page -- and not coincidentally, take a great deal more concentration to wade through and evaluate. Possibly the deciding factor: it's free (at least for students -- I haven't looked beyond).
AMA:
I got bored, looked at the fee, and stopped researching. Maybe somebody else can chime in about what they're all about. My feeling is that there'll be plenty of time to look at them when I have a salary.
Bear in mind that this is only what I've read online -- you should do your own research, I'm not an expert, etc. Know what you think before you show up.
hopefully you'll be getting lots of info on where to live/eat/study/go out, how to study, what books are necessary, etc. before you start. 
