I think a lot more played into the revolutions you listed. Many more countries have lost wars and/or lost significant overseas holdings without political upheav

I think a lot more played into the revolutions you listed. Many more countries have lost wars and/or lost significant overseas holdings without political upheaval. The USA lost (or walked away from) multiple wars since WWII with negligible political consequences. Britain, Spain, France, Portugal, Belgium all lost their overseas colonies, and only France had significant upheaval clearly related to losing Algeria. I don't see a tendency in your list, rather some examples where populist revolutions took advantage of a weakened and discredited regime. I could list quite a few more populist revolutions and civil wars that did not follow military losses. Russia almost certainly faces a bigger risk of internal convulsions and populist revolution than the US or any western European country. Putin has apparently staked everything on winning in Ukraine, so a loss or even a stalemate might very well topple him and his regime. Russia has a history of populist revolutions, the USA does not. I think losing Europe seems farfetched. Russia can barely maintain a war with a weaker country with a long land border. Europe and NATO have a lot more resources and advantages such as the superior US and British navies. Russia is surrounded by neutral or hostile countries, many of which have American/NATO missiles in range, but the USA does not have that problem. The bases the US maintains in Europe exist primarily to oppose Russian (formerly Soviet) expansion, so if Europe actually fell to Russia those bases would have no purpose anyway.