What is British slang for American?

I'm curious, when it comes to the colorful world of slang, what do the Brits typically call an American? Is there a specific term or phrase they use to describe their American counterparts in a casual or humorous manner? I'm intrigued to learn more about this aspect of cross-Atlantic linguistic exchange, as it often reveals fascinating cultural insights. So, if you're in the know, what's the British slang term for an American?