It may sound biased because I am an American, but I think our language, and dialects of said language are among the easiest to understand in the entire world, since most people I know talk slow and plain as can be.
Depends on which "American" accent you're talking about. Some "American" accents are unintelligible!
In the South you have about two to three dozen distinct accents.
In Eastern North Carolina you have the guys with marbles in their mouth. It's hard to even try to type how they would talk!
In Georgia you have several distinct accents. From the sing-songy "Gone With the Wind" to the folks who never move their lips when they talk and speak from the throat.
In parts of Louisiana you have Adam Sandler's Cajun man... hooowee!
Texas and Oklahoma have accents that range from chicano to a singing cowbow.
Lets not forget the Minne-sow-ta sweedish accent dont-cha-know where Olie and Leena roam.
In Appalachia you have all sorts of interesting accents some of which require a day to get your ear tuned right, making "Sgt York" sound like a thespian.
Pennsyltucky has a real wide range
In the East youse got dous guys dat talk like they come from da Joe Pecci school of diction to the folks that sound like Chaaarles Emerson Winchester the Therd. And of course the folks that paaahk their caaahs in Haahvaaahd and never do it Hawf-aahsst. Youse also god da guys for New Yawk. Other Easterners have the "idear" from time to time. (the conservation of Rs theory for the easterners...they add it in places and drop it in others.)
Not to start a holy war, but "American" or North American TV English is really a caucasian Midwestern thing (Pittsburgh through Columbus skipping parts of Indiana to Chicago and central Illinois, through Iowa Missouri, Kansas Nebraska, the Dakotas, and save the "oots" of the canadians, Manitoba & Saskatchewan, perhaps Alberta). California and Nevada too because of all the migration there from the midwest. Even where I live in Cinci is "American", but go a little further (or in that area Farther) to the southwest within the city and you have the german influence... "please" means "pardon me" when you didn't hear some one correctly. And go a little to the southeast in the city and you get appalachian influneces in the speech. Never mind 20 minutes south from my house in KY where they have a water tower that says "Florence Yall". The joke in this town is that Vine Street (which runs down the middle of the ciity north/south is a dividing line and residents from one side never cross to the other!
Anyway, not all "American" English is all that intelligible to even an American!
See ya
Tony
