"Interesting that there's the idea that "people are nicer over there"."
Possibly applies to urban cycling more. I found Copenhagen to be the most relaxed cycling imaginable. Yes there were a lot of segregated routes, but also a lot that weren't, and obviously junctions to cross. On numerous occasions I was passed by a car then indicating to turn in ahead of me - even the ones that could have turned without any allegation of a left hook then stopped to wait for me to pass the junction. This, I guess, is what I'd count as 'nice', and certainly appeared to be the norm over there.
I found the same attitude of drivers in Paris of all places.
Amsterdam was more mixed. Lots of close passing on the shared areas, and even saw a moped rider effectively shove a cyclist out of the way to squeeze between him and a bus.
People most certainly are people everywhere, but I still think that overall in the UK there's a bit more of a me me me attitude of drivers than there is in Denmark (or the Netherlands, or France, or Italy). Nowhere will be perfect, as your experience shows, but lots of places will be better, and aiming for better (rather than an unachievable perfection) will always contain a certain element of changing driving attitudes as well as decent infrastructure (unless we have a segregated lane beside every single road in the country, with little bridges over junctions).