I dont understand americans

Reminds me of a joke:

Johnny AND THE CLOWN
Johnny is poor and has been all his life. He doesn't mind it much, except for the fact that every year when the circus comes to town, he never gets to see it. The years pass and every year he watches the circus come and go with a tear in his eye. Then one year as the circus is leaving, he snaps. "Fuck it," he says." I'm going to get myself a job so I can see the circus."

The next day he applies for a job at a supermarket stacking shelves. He gets this job and works his heart out. He works every night stacking shelves, earning money. He spends very little, and saves heaps. He is the best worker the supermarket has ever seen. A year passes, and the circus comes to town.

As soon as the gates to the circus open, Johnny races up, first in line to buy a ticket. the excitement overwhelms him. He walks around the circus. He sees the animals, the freak show, buys a hot dog, plays on the clowns. And then he sees it, what he's been waiting for all these years...The Big Top.

Johnny races into the tent and takes a seat. Pretty soon the tent fills up and the show begins. It's a packed house and the buzz is electric. The dancing horses come out, then the elephants, then everyone's favorite, the clowns. The clowns run around and do their act making everyone laugh. When all this is finished, the head clown picks up a microphone and says "Now we'd like to pick a member of the audience to help with our show."

All the lights go out and a spotlight circles the crowd. and, as luck should have it, it lands on Johnny. Johnny is ecstatic, he nearly shits his pants with excitement. He can't believe his luck. The head clown comes up to him and says..

"Hey mister, are you the horse's head?"
"No." Johnny replies.
"Are you the horse's ear?"
"No"
"Are you the horse's tail?"
"No"
"Then you must be the horse's ASS!!!!"
And then whole tent erupts into fits of laughter all of Johnny's expense. Everyone is laughing, except for Johnny. He's as pissed as fuck. He vows then and there that next year, when the circus comes to town, he'll get his revenge on the clown.

As he's walking home, still fuming from the humiliation that the clown caused, Johnny thinks of ways that he can get back at the clown. Death, violence, poisoning....and then it hits him. Johnny will give the clown a taste of his own medicine. Next year, Johnny will blast the clown with the biggest insult ever!

The next morning Johnny flips through the phonebook looking for someone who can help him with his revenge. Then he finds an ad.

INSULT SCHOOL
Sick of being picked on? Come to our school and soon you'll be verbally attacking people with vigor!
'This is just what I need!!!" says Johnny. So he rings up the school and enrolls the next day.

So every day Johnny goes to the insult school, studying hard so he can learn the best and most harsh insult so he can get back at the clown. On top of this, he still stacks shelves at the supermarket to get the money for the circus. Day in, day out Johnny works his ass off.
Then his day arrives...

As soon as the circus opens it's gates Johnny barges to the front of the line, pushing people out of his way. No longer is he a kind, considerate man. He's a pissed off m.f. hell bent on revenge. He give the ticket seller the money, snatches the ticket and storms off.

He sees all the regular shit. The animals, the freaks, the clowns. He's so excited that he goes into the Big Top an hour before the show starts, just so he can get a good seat. The tent begins to fill up and the show starts...

The dancing horses come out, Johnny yawns. Then the elephants, Johnny tries to stay awake. And then the act Johnny has waited a year for, the clowns. The clowns run around and do their act making everyone laugh. Johnny wonders why everyone is laughing, it's the same shit they did last year. When all this is finished, the head clown picks up a microphone, exactly the same as last year, and says "Now we'd like to pick a member of the audience to help with our show."

All the lights go out and a spotlight circles the crowd. and, as luck should have it again, it lands on Johnny. Johnny is sits cool, calm and collected. The head clown comes up to him and says..

"Hey mister, are you the horse's head?"
"No." Johnny replies.
"Are you the horse's ear?"
"No"
"Are you the horse's tail?"
"No"
"Then you must be the horse's ASS!!!!"
And again the whole tent erupts with laughter. Except for Johnny. He sits there staring straight at the clown, a look of pure evil and hate on his face. The laughter quickly dies down as everyone knows something is going to happen. The crowd watched. This is Johnny's moment. He takes a deep breath, looks at the clown and says...

"FUCK YOU, CLOWN!"