The large European states are losing their cultural coherence.

I'm not so sure. Yes, there are strong pressures to acculturate large European nations and European institutions have indeed been skewed towards that goal over the past 30 years. But there's an ocean between trying and succeeding, and it's the kind of gambit which is very dangerous to try and loose.

To maintain it, they will be forced to trample on people's rights.

You are perfectly correct and this is exactly what will happen.

When that happens they will no longer be worth living in, if what one cares about is the democratic state as opposed to the nation.

The nations will win. They always do. Otherwise countries like Poland or Ukraine would have disappeared a long time ago. It's not meant personally but your opinion on that matter has no importance, no more than gravity cares about your inner feelings.

F = G.m1.m2/r^2 whether you like it or not.

Now, you can choose to feign and ignore that fact and, when it hits back in your face all the harder that you tried hard to ignore it, you can regret and decry it, but it will still be your deliberate ignorance that will be at fault.

Robert Schuman was right when he said that if he had to start over, he would start with culture. Too bad alas he didn't see that at the beginning. De Gaulle too was right when he said:

Ce qu'il faut surtout pour la paix, c'est la compréhension des peuples. Les régimes, nous savons ce que c'est: des choses qui passent. Mais les peuples ne passent pas.

What we need above all to maintain peace is an understanding of nations. Governments, we know what those are: things that go away. But nations never go away.

I don't think there is anything ideal about nation-states but it's there and you have to do with them. The EU supranational utopia is not only an error but a perfect recipe for conflict and civil war. If, as I do, you want Europe, you have to build a European nation, to create a community of interests, a community of trust, a community of destiny. I don't see any of that on today's EU and that scares the crap out of me and it should scare you too.