In the way you mean it, I think the US is definitely in between England and Bulgaria. I think most British people tend to think of American culture generally as a lot more like ours than it really is. My guess or impression would be that 'culture of legality' level varies across the USA (just as it differs somewhat between England and Scotland, something the English seem to have a lot of trouble believing when I tell them! An Irish student though this year piped up to say she knew just what I meant, since Ireland was quite different from England, too). I'm only really familiar with the culture of the US South, especially Tennessee, but I think most of the rest of the country is also very different from England.
@pemerton
So, bringing this back on topic - given the lower levels of 'culture of legality' in the US, I think it's unsurprising that US based posters here would not see (a) the lack of legal merit in WoTC's argument as being particularly important, compared to (b) WoTC demonstrating that they are untrustworthy, bad faith actors. And then (c) it becomes very important to them that Paizo has established a reputation as a good faith actor (leaving aside some controversies which aren't that relevant).
I think it's not so much that people wrongly think WoTC's argument has legal merit, they just don't think that question matters as much as the question of trust. Personally I'm more with you in that I think it's vital WoTC's attempt to gaslight over OGL 1.0 Section 9 be comprehensively defeated. But I see where they're coming from.