Er, Int'l style Tango is as detailed as the other dances. Plus, there is NO rise and fall (contrary to the previous post).
Usually, Waltz and Quickstep are tuaght as the first dances to be learned. Tango is different from the others in that the technique required is different. Therefore, 'picking' an 'easy' dance makes less sense - picking a good COACH is the answer.
There is a lot to leasrn in American Style, too, you know... simply because you can 'do' basic actions in any technique does not mean that you have mastered or even scratched the surface of the dance. Good dancers will tell you that it's like peeling away at the surface of an onion - always more detail, etc. That's why you can never tire of dance - it's always got things to learn, always ways to improve.
Talking to a Bronze level IS dancer, you'll see one perspective - and a higher level dancer, another. Both are valid, but you can see that there is more to it than meets the eye.
My advice is to find a good coach. If you are in the midwest (where good Intl coaching is scarce and social American must be the major thrust of teaching; I presume that's why at the Nationals you see mainly seniors from Midamerica doing American) then I'd go to a USABDA regional competition and look at the Open level amateurs - and then ask the ones that do the best, who their teachers are.
If you are on the coasts, you will probably be exposed to Int'l coaches in your area. Be warned tho, that 'advanced' coaching does NOT mean more advanced than YOU but advanced compared to the local medalist level.
Good luck - you'll find International is very rewarding and excitin to learn and dance. You'll soon also find that your skill levels in International make you a desireable partner even at the local social - you will be learning movement and technique, which are the basis for real dance!