a. That depends on the relations with the US afterwards. For the UK example - think of their relations with Europe after 1945, before they'd entered the EU. It was fine. I mean, after 500 years or wars, but, you know, bygones. b. Isn't it more that the supremacist attitude fuels the secessionism, rather than the other way around? c. Secession from the US empire of some of these states might not be such a bad idea for those states.