"The Americans" joke

A man dies and goes to Heaven.
The angel Gabriel meets him at the Pearly Gates and takes him on a guided tour.
The man sees various groups of people all standing around and talking to each
other.
"These are the Buddhists," says Gabriel. "And over there are the Jews, and the
Hindus. Over here are the Muslims, and over yonder are the Jehova's Witnesses."
In fact, the man sees every religious group, every nationality, and every
culture in Heaven.
Eventually, the pair comes to a large wall.
"Hey, what's this wall doing in Heaven?" asked the man.
"SHHHHHHHHHHHHHHH!" said Gabriel. "Lower your voice. Behind that wall are the
Americans. They like to think that they're the only ones here."