"Yes, things have changed, but how did they work in the past?"
Mostly by having massive periodic wars. Seriously, Europe has rarely managed to go 50 years without at least two of the French, Germans, British, Dutch, Italians and Spanish being at war with each other. Saying 'we always managed fine before the EU!' neglects to note that immediately before the EU, Germany's main import into Britain was (quite rapidly-moving) incendiary bombs.