Most Helpful Guy
Big disadvantage (NB: based on Canada): If you sponsor a girl to come back home with you, you are obligated to the government to support her for x number of years, even if the relationship breaks down.1
Most Helpful Girl
You don't marry a "foreign girl", you marry a specific person that you've hopefully chosen because of who they are rather than the fact that they're foreign.
Anyway, the only advantage I can think of considering your question is the fact that if you want to live within a certain culture (alongside the American culture) and still physically remain in the US then you can bring a foreign person from that culture. :/ But that's still debatable.1