In particular, I'm looking for American citizens who at a fully mature age took up citizenship in a foreign country, served in a very high position in the foreign government, then attempted to take up a high role in the U.S. government.
The high-ranking officials to have arrived at the oldest age include Zbigniew Brzezinski, who arrived in the U.S. to get a doctorate at Harvard after obtaining a bachelor's and master's at McGill in Canada. Zalmay Khalilzad's career is similar. Some others arrived around age 21, such as refugee Michael Blumenthal who then went to Berkeley as an undergraduate.
Don't say that he's hypocritical,
Say rather that he's apolitical.
"Once the rockets are up, who cares where they come down?
That's not my department," says Wernher von Braun.
The point is not that Fischer arrived in the U.S. at age 23, but that he left the U.S. at age 61 to head up a key department of a foreign power but now he wants to come back at age 70 to take a crucial position in the U.S. government.