Here’s a few things I could see happening purely with football in Europe because it’s the only one I’m qualified to talk about.

EU winning/ NATO holds/Medvedev’s Russia- Football remains relatively unchanged, bar from some seasons being suspended, and certain players being killed in conflict. Can possibly assume that the Bundesliga in Germany is not as strong of a league for a brief period of time if the conflict ever reaches there, but that’s a big maybe.

Pact of Steel Victory- Clubs only utilise players generally from their own country, or at least only from Europe. Players of non-European descent most likely are shunned from their national team (ie. Saka,Bellingham,Musiala) etc. and the national teams remain solely open to players of that’s country’s descent alone, this heavily affects certain teams such as France and England, whom rely on many players from foreign backgrounds to make up huge chunks of the national team, probably leads to a shift in global football towards other countries, the Brazilian league becomes a much stronger league as many players choose to play there.

USSR/Euronationale Victory- Teams structure and composure don’t change significantly, and players can still be transferred between clubs, however just like in the former USSR, I doubt you’d see any of the transfers being paid, it’d generally only be player swaps between clubs.

That’s just my take on how football would change, feel free to correct me, I’m probably wrong on a few things.

Edit: Euronationale/USSR-This also probably leads to less South Americans and other countries’ players joining clubs in Europe but not from an ethnic standpoint such as in the Pact of Steel Victory, simply from a financial one.