I'm not a yank, and i'm not thick and i find it very funny. although i'm not sure if you're asking why friends is funny or why the year it started in is funny ;)
the first episode aired on the 22-Sep-1994. friends is brilliant and has been from the start. I mean where would most pathetic man be without the pick up line "How you doing?" or where would over bearing clean freak women be without Monica? and where would the hair gel companieds have got their income from without Ross. Hooray for Friends.