Doesn't seem like the main reason why they got upset was because she was American

The Yale University professor's former ties to Big Tech companies including Microsoft and Apple raised eyebrows, as she would have been in charge of advising on the Digital Markets Act, the EU law designed to tame those very companies.

Also, would you hire a EU national who would have worked for years for EU car companies to regulate the US car market?

EU not wanting an ex-Apple and ex-Amazon Lobbyist as EU's Chief Economist in charge of enforcing EU's fair market competition laws has absolutely nothing to do with xenophobia.