Interesting.. see I"m pretty much the exact opposite in thinking. I don"t really care about ethnicity (ie, european, asian, caucasian raised on the moon etc), but I really don"t prefer american girls at all. Someone said it earlier, but the way in which our culture raises people imho is a little fucked up when you apply that thinking to extending relationships. That rabid individualism and radical hedonistic tendencies makes it very, very hard to establish a type of relationship that"s meaningful and can last a long length of time.
Why? Well we"re bred to think of ourselves first. What"s good for me? What"s in it for me? What does this person do for me? The second there are doubts (and of course there always are the longer you"re in a relationship... it"s a function of time) americans will typically start to look for something else or mentally or physically wander instead of trying or even wanting to reinforce what they have. I"m not saying this is bad.. I"m just saying that"s how we"re raised as a culture. That hedonism really comes out when you talk about relationships in America, and all you have to point to are numbers like divorce rates.
This leads to, obviously, lots of drama, back and forth relationships, multiple relationships, and everything else in between in the lives of most Americans.
I mean that"s fine if that"s what you want, but that"s why I said asians are probably superior for longer-term relationships (not americanized asians).