re: Poker & USA players vs Rest of The World!
I think OP has some kind of a point (at least for some years ago).
Very often when US players are asked how they got into poker, the answer is like:"well as a kid we often sat around the kitchentable playing stud or 5-card draw".
So I guess a lot of the players know more than just Holdem.
Now take the Netherlands
There always has been a lot of cardplaying, all kind of games, but poker was not very common or even rare.
Only after the beginning of the pokerboom, poker became popular, but for most people it's just holdem.
So, simply said I guess a lot of US-players started playing holdem with much more of a poker background than a lot of players in ROW.
I also believe that has changed over the last few years as I think a lot of the young guns nowadays ,no matter where they come from , just start their carreer playing holdem, .