The European Union will have some pretty extensive reforming to do once the Ukraine war has ended. I doubt the EU will dissolve, but I'm pretty sure it be quite different from how it is now.
If we assume the current (relative) unity will last for a decade or so while Ukraine is rebuilt and we get waned of fossil fuels, then we'd have to start preparing for internal political shitstorms '32, as there'll be a lot of elections '33 and '34. If we make it past the EU parlaiment elections in '34 I'd say we're good for a while after that.
Edit: But yeah, things definitely go up and down in cycles. No doubt about it. No single nation state will remain forever, but the entire latin-anglo-slavic-germanic-fenno-ugric clusterf*k we call European civilization won't just go away within such a short timeframe. An eventual decline will take many decades, if not centuries.
I don't think there will be a USA (in its current borders) in 2030-2035. The EU won't make it either, it's just too dysfunctional.