Sadly, many stereotypes have a basis from truth.
With Americans, there's no one culture really any more. It's a big country and there's regional differences for starters. But also even within those smaller regions, there are other divides.
I'm from North Carolina and I often joke there are three states here...the conservative/provincial Rural, the Mundane Suburban, and the progressive Urban. And really, you'll probably find similar divides in many other parts of the US too....although I admit I'm simplifying things greatly.
As a gay man (and poly!), I try to avoid the provincial, conservative and mundane areas as much as humanly possible. I only really feel comfortable in the cities and other progressive or enlightened areas...they tend to be less likely to reflect those negative stereotypes you mention.
And of course the education level and religious beliefs make a huge difference too!
Sadly, many Americans will find some of these opinions "elitist" or whatever else Fox News tells them to think....but really, it's what I personally observe on a regular basis.