An American spy in Moscow

 An American spy in Moscow walks into a bar, but the bartender gives him a suspicious glare. "Are you an American spy?"

"Of course not!" replies the American in perfectly fluent Russian. "Could an American do this?" He grabs a bottle of cheap Russian vodka, pours himself three shots of it, and downs them without flinching.

"Good point," replies the bartender, "but I still think you're a spy."

"Could an American do this?" He picks up an accordion and plays some folk songs on it like he'd heard them his whole life.

"Still think you're a spy."

"Could an American do this?" He stands up and flawlessly dances the kazachok.

"Still not convinced, you're definitely a spy."

The American throws up his hands in frustration. "Why could you possibly think I'm an American?!"

"Well for starters, you're black."

Variants may change what the American spy does to try and blend in, or who is the one that calls him out.