In what way was WWII an "extrapolation of empire?"

The EU and its predecessors came about largely as a reaction to wars in Europe. On the whole, the peace has been kept. You can only be in the EU if you are a democracy and sign up to conventions on human rights. Democracies do not go to war with each other on the whole. Oh yes, Teribus claims that it's actually been NATO who's kept the peace. Whether he's right or wrong (he's wrong, as with everything else), Trump isn't up for NATO, is he? Better pray the EU survives. With us still in it, preferably. Both the Islamists and Putin are flexing their muscles, and a nice bit of US protectionism might make China become not very nice.