It is good to be proud of your heritage, but your either American or your not. There are no hyphenated American countries.
I bet many of them would have loved to have been on the US team but were not given the opportunity, so they went to where they thought they could get on a team. For them it is their livelihood (think food on the table), not an issue of patriotism. In a way, this insures that the USA receives the best of the best and the other countries receive people who are good but not as good, as we had first pick.