As far as we are concerned, America did not provide war materials out of the goodness of it's heart, it sold them and got very wealthy indeed on the back of the Second World War.
As you say, much depends upon one's perspective. The various manufacturers did indeed make money. The US government, on the other hand, was the guiding force in assisting in this trade. From March of 1941, before the US entry into the war in December, the US government was actually paying the bill (meaning US taxpayers) to 'lend-lease' material to the Allies. It was this move away from official neutrality which caused Germany to begin to attack US merchant vessels, which they had previously shied away from. The idea was that the Allies would repay the US, which paid the manufacturers. However, the debt, over 5 Billion US dollars, was negotiated down to 1/5 of that, and most country's debts were completely forgiven (not the UK or USSR). That still means that the US taxpayer paid the majority of the cost to the US government to purchase and ship war material to the Allies prior to the entrance of the USA into WWII. All equipment that the UK decided to keep after WWII was sold for 10% of the initial cost to the US government.
So yes, the manufacturers got wealthy. But not on the backs of the citizens of the UK and other Allies. On the backs of the US taxpayer, as a matter of US policy changes. So one can indeed argue that it was 'out of the goodness of our hearts'.
I do not mean to imply that to do so was wrong, for we (and the French) have also done very nicely at times out of selling arms to both sides of a fight. Business is business and those raking in the cash don't much care where it comes from or how much it costs their customers in 'assets' that aren't measured in gold.
Lend-Lease, however, wasn't a gift, it was a contract. It can be argued that the terms of that contract were generous but it still took us fifty years to pay it off, crippling our post-war economy to do so. Further, we handed over all our scientific and military advances; stuff that was radically advanced for it's time. An implicit part of the deal was also that we, the British Empire, ceded our sphere's of influence in the Great Game to America once hostlities ended.
Indeed. And was this not desired at the time by both the UK and the USA? We were left as the 'Arsenal of Democracy' and seen (rightly or wrongly) as the world's policeman. We were, along with the Soviet Union, the first two 'super powers'.
As to the postulated invasion of the UK, it is generally concluded that that was prevented by the RAF - a little affray called the Battle of Britain. It is true that the supplies coming across the Atlantic were important in keeping us up and running up to that juncture as things hung on a knife edge. But again, those supplies were not a 'freebie' and it is likely that if it were not for the close ties between Churchill and Roosevelt then even that mercantile trade would not have occurred. After Operation Sea Lion was called off, Hitler's attention swung East and never really re-focussed our way.
You may be right, I concede you have a valid point there. On the other hand, there is no way the UK could ever have mounted an invasion of Europe from the UK without the USA's massive manpower as well as material, so the best that could have been achieved would have been what; detente with Hitler? And Hitler showed such a propensity to respect declarations of neutrality; over time, he abrogated every single agreement with respect to non-hostilities and non-invasion pacts that he ever made, with the exception of the Soviet Union, who broke the agreement first, as I recall.
What I'm saying is that if WWII had ended with German hegemony in Europe, sooner or later Hitler would have turned his eyes to the UK. He did not have a strong sense of restraint.
It cannot be overstated that without American material involvement in the Second World War (and man-power in the First) the course of things would have been very different. From our, British, perspective whether they went better or worse for us is a matter of conjecture, odd as that might sound to American ears.
The same can be said for our having had Churchill as PM at this crucial juncture. Tho' he is lauded as a Collosus-like hero of the C20th, there is a definite case for arguing that we would have been better off without him in the long run, for he destroyed the Empire he professed to love. It was only his implacable resistance that prevented Britains coming to terms with Germany and forced Hitler's hand into considering invasion in the first place, for the Fuhrer was actually something of a fan-boy of our Empire and would have much preferred to have us on his side! What an alternative history novel that would make

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My reading of history has caused me to seriously re-evaluate Chamberlain's despised status within it, but I am not yet ready to concede that Churchill was the wrong man at the wrong time for the UK. As I mentioned above, I suspect that a separate peace with Germany would have lasted only until the rest of Europe was pacified and hostilities at least on a low boil with the Soviets. I do not believe Hitler would have let the UK alone, under any ideal circumstances, for any period of time.
As to peace in Europe since then, well, aye, other than the Balkans (which have always been aflame to one extent or another), things have been quiet. I don't believe that that is entirely because our governments have learned the true futility of war. The fact that centuries of increasingly bloody conflict has drained the coffers dry of gold and blood has a lot to do with that I feel - that and the Cold War ... and MAD of course

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We, the USA, are painted as the war-mongers, and Europe is a peaceful place. So Kosovo is in Kansas, right?
I still must return to my thesis, then. There have been precisely two World Wars. Both started in Europe and by Europeans. No US machinations have been complicit in the beginnings of either one (although the Japanese war on the USA, which devolved into the general World War, was based on US and other Western powers' imperialistic land-grabs in the Pacific).
We are not the starters of World Wars.
We have also had a historical tendency to be militarily non-interventionist if not exactly neutral in our dealings with the world. Our populace has preferred to stand alone for the majority of our existence. We are castigated when we step out of that role; we are castigated when we cleave to it. Yet we're not the ones who start the big wars. I conclude that there is something not logical about this picture.