I agree with you 100% on the "backfire effect", and I think it's not really difficult to understand the mechanism behind it. But I don't think the US is really much different in that regard than anyone else, the differences there are maybe cultural at best, but in any case superficial. E.g. when I was looking at a flat in Germany, a landlord told me he subscribes to many newspapers, including the Süddeutsche Zeitung, but only to "monitor the left". That person identifies clearly with the right, and it doesn't matter how he phrases it.