A. I'm fairly sure that the British are stereotyped by other Europeans as being ignorant about other cultures. In fact, I think you guys get tabbed with a lot of the same negative stereotypes that you try and hand out to the Yanks. Yes, Americans are a bit ignorant of other cultures. I would have to get in my car and drive for hours and hours to get to a different culture (French Canada). That's the case for most Americans. Our culture is also the dominant world popular culture, with a bit of help from you guys. We aren't watching French and Chinese movies. Everyone is watching ours.
B. It's very British to over obsess about the influence that certain boogiemen have on American culture. I'm not sure why you guys pick these certain boogiemen to fixate on, but perhaps it's those middle America porn shows that seem to be produced for British consumption. Perhaps it's that you're consuming US based news produced in liberal bubbles. Our coastal liberals often have very poor perception of what's driving issues in Kansas or Arkansas. Fox News has around a million viewers per day. The average age of their viewership is around 70 years old.
C. Ignorant conservative whites might think the UK is on the verge of a race war, but liberal whites who watch MSNBC aren't any better informed. They often think your island is filled with classy, intelligent, and peaceful people of all races living in perfect harmony, and the only thing stopping that dreamworld here in the US are the existence of bitter, conservative, and uneducated whites. The reality is that white flight has struck large parts of England, destroying generations of social bonds in a short period of time. The reality is that there are large portions of the immigrant communities from the past few decades who live segregated lives incompatible with Western culture and are a net economic drain on the country. Tell this to your average white liberal and they think you're lying.