⁠Britain’s King Charles and Queen Camilla arrived in the United States on Monday for a four-day trip, welcomed by self-proclaimed royal fan Donald Trump even as the US president has differed with the British government over the Iran war.

The state visit, by far the most high-profile and consequential of Charles’ reign, marks the 250th anniversary of the US Declaration of Independence from British rule, and is the first to the country by a British ‌monarch in two decades.

After landing at Joint...