One could write a book to fully address this question. There are many ways in which they contribute positively and many ways in which they contribute negatively. I am not comfortable approaching it as a simple yes or no.
You're joking? You seriously think that the existence of American universities has an ambiguous effect on the US as a country?
That anyone would even consider that is one of the most moronic things I've heard. Jesus Christ.
Would you say that still if colleges suddenly started acting like Bob Jones or other Creditless Christian Schools or if University of Phoenix types became even more prominent than they already are?
Not hard to deny the current system is deeply, deeply flawed.
Doesn't mean the positive don't outweigh the negatives of course.