With a POD no earlier than January 1st, 1900, make the United States of Europe a reality. Good luck!
A minor nitpick: State. Nation is, er, ASB (to exemplify: in OTL 1988, Germany was two states but one nation).Mmm, yes, sorry about that. No, it doesn't have to have that name, but it must be a coherent nation with a central government. The minimal extent is from Poland to Portugal, while the maximum extent is Russia and Turkey to Portugal. It doesn't have to include Iceland, the UK, or Scandinavia, but extra points if it does.
Actually, Pan-Europeanism, as a vague idea, was already floating around in 1900. In fact, the term United States of Europe, used by Europeans, dates back to the 18th century (if not by much of a margin). Beyond that, the limitation is that POD must be within the limits of this forum. It doesn't say the POD has to be that early, or that the federation can't be a recent establishment in that TL's 2010.The biggest problem here would be overcoming the nationalism peaking in Europe at the time.
Remember, Pan-Europeanism is a very recent development - after all, a couple of centuries ago they were killing each other over not letting one country gain ascendancy over the others.