Interesting: lots of NYC swung massively toward Trump between 2016-2020, while most of Boston swung Democrat.
And Dallas starkly shows the shift of 2020: the white suburbs got dark blue and the the bluest parts of the city with the highest black population swung toward Trump. First map is 2020 results, second map is change from 2016.
I guess we shouldn't say they got dark blue. They shifted just barely to put Democrats over the top. A very weak shift to base an entire party identity around.