Compared with many countries around the world, the US is still a great democracy, but a much lesser one than it was four months ago. The constitution has not been rewritten. Checks and balances have not been dissolved. The difference is a president who ignores those constraints, and the impotence of the institutions that should enforce them. Which is the true US, the one enshrined in law or the one that smirks in contempt of law? If the latter, should Britain welcome its embrace as a kindred nation? That is an existential question lurking in the technical folds of a...