The one thing about America, is that we are not all the same. If you heard me speak, you would hear clear enunciations. I will sometimes write in slang, for effect, but I do sometimes hear people talk as you have described. But, in no way is there anything linguistic that unites Americans.For some reason Americans have a problem with the letter 'T'.
Internet becomes innernet, duty become doody etc. I'd love to hear an American say "...yes, it's a metal medal he was awarded..."
And, in separating from Britain, yes, we decided that we were no only going to rise up against the monarchy, but that we would also establish our own rules to our language.
But still.... chlorine wash?