i think you got it a bit mixed up, and it's ok, there's too much info out there.
there are a lot of players in national teams that play "abroad" with respect to their home countries-- especially those in poor countries or those who don't have very strong professional leagues. e.g., the best american players don't play in the MLS, but abroad.
eg, tim howard was born in brunswick, new jersey:
http://en.wikipedia.org/wiki/Tim_Howard but he does play in england.
see more info here:
http://en.wikipedia.org/wiki/United_States_men's_national_soccer_team
of course, 'merica being a country of immigrants and having little soccer tradition, it's going to have imports (real imports) in the team, but not nearly as many as it used to have back in the day. e.g. feilhaber was born in brazil but moved to the us when he was 6 (oh my! foreigners!) but no, in reality what you have lots is kids from immigrant parents.
most soccer teams however it's 100% national meat. seriously. well, england's got an italian coach, ha ha ha...
now, while most if not all of the italian national team plays in italy, the PROFESSIONAL italian teams are full of imports. check out the inter milan, current european champions:
http://sports.yahoo.com/fbit/teams/int/roster
that's a truly international team, eh? not a lot of italians. but if you search well, you'll find materazzo there, who played for his national team today. the other dudes are with their own national teams, e.g., lucio, who is the captain of the brazilian team. all very complicated. yet, all of the brazilian national team are native brazilians.
now, if you think about american sports-- how many native californians play for the l.a. lakers?
anyway, im tired, gotta go crash early today. but don't let this import theory kill your enjoyment of ritual world war! it certainly beats nukes.