WASHINGTON — President Trump has made a trademark of upending many of the diplomatic traditions that have defined American foreign policy for decades, angering a host of longtime allies. Now, a growing number of his ambassadors are doing the same.

This week, Richard Grenell, the newly installed United States ambassador in Berlin, outraged some in Germany when he told Breitbart London that he wanted to “empower other conservatives throughout Europe,” a direct political threat to Chancellor Angela Merkel’s governing coalition. Germany’s Foreign Ministry asked for a clarification.

Last week, David M. Friedman, the ambassador to Israel, told an Israeli newspaper, “There’s no question Republicans support Israel more than Democrats,” making an explicitly partisan argument that is generally forbidden among ambassadors.

And earlier this year, Peter Hoekstra, the ambassador to the Netherlands, refused to respond to a room full of Dutch journalists who asked him to clarify false statements he had made in 2015 that politicians and cars had been burned by Muslims in the country. He has apologized.