While I used to say exactly that for most of my life, trust me this is a gross oversimplification. With an emphasis on gross. Law traditions date back to the Romans, Celts, Germanics and others at least. And of course no sovereign country on the onset of the EU would have accepted the new EU norms if they were to contradict with their own. That the EU nowadays tries to impose rules that contradict those norms is reason for the ever rising resentment of Brussels around Europe.
> If we could avoid having to invade Ireland
You say it yourself: How can we declare moral superiority if we are openly discussing invading Ireland because we've abandoned pillar principles like national sovereignty?
How can you lament "over hundreds (or even thousand) of years in Europe [of] warfare" while simultaneously abandon the core lesson of those wars (sovereignty)?
I mean the EU, the free market, the euro, all that doesn't have "hundreds of years of cultural norms and customs" behind it. Why couldn't we go further? The only thing that we've had consistently over hundreds (or even thousand) of years in Europe is warfare and royal inbreeding. If we could avoid having to invade Ireland or having our finance ministers wed each-other in order to settle this tax dispute I think it would be grand.