Many europeans simply won't support the way the US deals with issues like guns, healthcare system, their hard-on towards privatisation, how religion is deeply inrooted in their politics, etc. And this is just social stuff.
mz: The "American System" is such a broad term. What do you even mean by that? Explaining negativity you wonder about isn't difficult. There is more to it than just economics.
I am not negative about Americas, just supported their economy bought Rye whiskey and bourbon. But seriously I have issues whit one of them, otherwuse no,
to be honest I never understood the negativity of Europeans towards US. If nothing else, the American system has been extremely good for you considering that it has subsidized your lifestyle after the WWII.