What do you call the War in Cyprus and the Civil War in Northern Ireland? Turkey and Greece are two separate countries involved in territorial war of Cyprus (sometimes considered Western Europe). UK and Ireland are also two separate countries definitely inside Western Europe. Algeria and Angola were an integral part of France and Portugal respectively, just like Lyon and Lisbon. To the European powers, these were wars inside western European countries.
I find your specification of "War" and "Western Europe" awfully convenient. For example USA had hegemony over both the UK and Argentina, yet the latter invaded a territory of the former, but you are still correct because the Falkland Island aren’t in Europe.
If history doesn’t fit your narrative, you can simply narrow the scope until it fits. This is the problem with grand historic theories, they always just fit, but only after being hammered to the "correct" shape.
> Turkey and Greece are two separate countries involved in territorial war of Cyprus (sometimes considered Western Europe).
If you want to consider Turkey part of Western Europe that’s up to you.
> UK and Ireland are also two separate countries
The UK was not at war with the Republic of Ireland; it was at war with domestic terrorists inside Northern Ireland.
> I find your specification of "War" and "Western Europe" awfully convenient.
If that’s true, I’m sure it’ll be just as easy for you to find another 78 year period of history in which no two sovereign Western European polities went to war with one another. In fact, the whole reason I pointed it out is because the western half of Europe had been interminably war-torn for centuries. You’re talking about colonial wars in Angola and IRA terrorists; I’m talking about breaking the centuries-long cycle of Anglo-German-French wars that stretches into medieval times.
> For example USA had hegemony over both the UK and Argentina
You were the one that stated that USA had hegemony in Western Europe post 1945, so that should include the UK. The Argentinian dictatorship had strong USA backing, the dictator who initiated the invasion Leopoldo Galtieri was a graduate from the US Army School of the Americas, in fact Argentina was working with the CIA in their backing of the Contras militia in Nicaragua. USAs influence over the Argentinian dictatorship just before the invasion is no secret.
As we see, USA hegemony is not sufficient for peace (even your very convenient definition of peace). However it is still not established that USA hegemony is even a necessary conditions.
First, you can mark any large cross-national territory over any arbitrary decade and find peace. Even territories with a history of war. For example, there hasn’t been large South American countries going to war with each other since 1947 either (see I can conveniently omit the Falklands War too if it fits my narrative). Heck, even the African great lakes has seen peace according to your definition since Tanzania invaded Uganda and disposed of Idi Amin in 1979. I guess Tanzanian hegemony is a thing for good.
Second there are multiple alternative hypothesis you haven’t explored. Don’t you think the UN deceleration of human rights helped with minimizing conflicts, the rise of democracy, the end of imperialism, decolonization, demilitarization, buildup of infrastructure, the European Union, etc. I find these together way more plausible then your supposed USA hegemony.
> USAs influence over the Argentinian dictatorship just before the invasion is no secret.
That doesn't imply that the US had any hegemony or control over Argentina.
> Don’t you think the UN deceleration of human rights helped with minimizing conflicts, the rise of democracy, the end of imperialism, decolonization, demilitarization, buildup of infrastructure, the European Union, etc.
Why did all of these things happen in the first place? American hegemony. You can tell because Europe tried half of the things on that list after WWI but they didn't work.
> Why did all of these things happen in the first place? American hegemony.
This is a theory, not a really good one, but lets take it at face value, starting with the end of imperialism. Given that USA continued it’s imperialism after WWII while WWI is the beginning of the end of imperialism for Europe. The British empire stopped existing in 1998, but I’d say the end of British rule over India in 1947 was the peak for the end of European imperialism. This had nothing to do with USA.
Decolonization: This didn’t happen until the 60s and only after fierce resistance from indigenous people withing the colonies. While the USA held a powerful seat the UN that called for decolonization, the fact that USA held its colonies (e.g. Guam and American Samoa), and that it took fierce colonial wars before liberation, I say indigenous resistance had way more weight than any USA influence of the matter. Portugal didn’t actually relinquish their colonies until their dictatorship fell in a socialist revolution in 1974.
Rise of democracies: Again did not follow USA occupations. Staying within Portugal, The Carnation Revolution would certainly be the first time the USA backed left leaning armed forces against a right wing dictator. And we know they didn’t, USA stayed out of that one. Greece on the other hand didn’t became a dictatorship until after it had joined NATO. Now this dictatorship was no friend of the USA, but that only further proves how little USA hegemony had in preventing these dictatorships and in the rise of democracy. I would actually give the EU more credit here. Speaking of which,
the EU: I honestly don’t know how you can give USA hegemony credit for this. It started as a free trade agreement, USA didn’t start doing anything similar until 1994 with NAFTA. Stating USA hegemony here is frankly a little insulting, insinuating that Europeans cannot take autonomous decisions regarding their own affairs.
The only think we can definitely thank the Americans for is demilitarization and the initial buildup of infrastructure.
But I think you get the point here. Attributing all of these to USA hegemony is a very simplistic—and frankly wrong—view of history. Honestly at this point I can’t tell what you consider hegemony, if USA had hegemony over Europe since 1945, how did it not have hegemony over Argentina during the dictatorship?
> The British empire stopped existing in 1998, but I’d say the end of British rule over India in 1947 was the peak for the end of European imperialism. This had nothing to do with USA.
Decolonization, including the dismantlement of the British Empire, was an explicit policy goals of the US dating all the way back to at least WWII. One of the signature examples of this orientation—and the first clear assertion of American hegemony even over Britain—was the Suez crisis.
> Rise of democracies: Again did not follow USA occupations.
The democratic governments of West Germany, Italy, France, Belgium, the Netherlands, Denmark, Norway, and Austria were effectively installed by the US and UK at the end of the Second World War. Without American involvement, none of these countries would have become democratic; they would have either remained fascist or become communist.
(This was not the case for e.g. Argentina, Turkey, or Portugal.)
> the EU: I honestly don’t know how you can give USA hegemony credit for this.
The core concept of the EU is the goal of establishing a “United States of Europe”. In other words, it is an attempt to emulate Europe’s hegemon, and it arose almost immediately after Western European democracy was installed by the Allies at the end of WWII.
I find your specification of "War" and "Western Europe" awfully convenient. For example USA had hegemony over both the UK and Argentina, yet the latter invaded a territory of the former, but you are still correct because the Falkland Island aren’t in Europe.
If history doesn’t fit your narrative, you can simply narrow the scope until it fits. This is the problem with grand historic theories, they always just fit, but only after being hammered to the "correct" shape.