As of this question's posting in Feb 2024, there are three US citizens that have given up their citizenship and become Prime Minister of another country:

George Papandreou, the Prime Minister of Greece from 2009 to 2011, relinquished his U.S. citizenship shortly before taking office. He was born in St. Paul, MN, when his father was a professor at the U of M.

Boris Johnson was a US citizen until 2016.

Golda Meir (née Malbovitch), the Prime Minister of Israel from 1969 to 1974, grew up in Milwaukee and became a naturalized citizen when her father became a citizen in 1917.