As an american, russian, jew, from a muslim/asian country, with a very soft spot for israel, I must admit while I try to be objective, it's possible at times I am inadvertently, though not intentionally, somewhat biased. Incidentally, I also spent my last vacation in Cancun Mexico, and have been a repeat visitor there
With that disclaimer out of the way, I still think israeli guys, whether it's a group of 3 or 10, are the most LOUD annoying, and friendly bastards you can come across. Military services does leave them quite a bit less inhibited than most people. I've had the pleasure of also dealing with groups of swedes, norwegians, germans, french (i love french girls, their accent should be illegal) and pretty much all former soviet block countries.
It's true, americans do tend to stay fairly limited to mexico and the carribean. It's mostly a matter of logistics. Traveling to australia or asia for example, means a difference of at least 12 hours, and 14+ hours in the air. So while I can hop on a plane from NYC in the morning, and be enjoying mojitos in a pool by mid afternoon in mexico, doing the same with say Ko Phi Phi (my favorite thai destination) means ~22 hours of travel and 12 hours of jetlag. It's just impractical given the custom of american vacations which are are only a week or maybe two weeks long.
I'm extremely torn currently on whether to book a vacation to asia, (vietnam or thailand) or go the easy route and do dominican republic currently.
As for Cancun, the resort areas specifically, it's a 100% artificial experience, and pretty much everyone, american or otherwise, sticks to the all inclusive resorts. That's kind of the whole point... zero stress, zero anything really, just beach, sun, pools, and as much booze and food as you can consume.