JD Vance joked at the National Conservatism conference last week that the UK could be the "first Islamist country to have nuclear weapons" in a jibe about the new Labour government.
The 39-year-old has been selected as Donald Trump's running mate for the upcoming election.
With nuclear weapons already at the UK's disposal, Vance appeared to joke that the country could be taken over by radical Islamists.
He told the National Conservatism conference on Thursday: "I have to beat up on the UK - just one additional thing. I was talking with a friend recently.
"And we were talking about, you know, one of the big dangers in the world, of course, is nuclear proliferation, though, of course, the Biden administration doesn't care about it.
"And I was talking about, you know, what is the first truly Islamist country that will get a nuclear weapon and we were like, maybe it's Iran, you know, maybe Pakistan already kind of counts and then we sort of finally decided maybe it's actually the UK, since Labour just took over."
