As for American students' writing ability, tell me how many American college students can tell the difference between effect and affect, their and there, its and it's. Dr. Higgins in "My Fair Lady" is correct: English has not been spoken (or written) in America for many years.
Shockingly ignorant, jarringly talkative, blithely mindless, intellectually depressing, and boisterously self-important - these are just a few words that come to mind if you ask me to describe what a typical American college student is. And yes, most of them are lazy, too. Intellectually and physically.