Well.... you have to take in consideration that the US got into WWII very late. So...I guess you have to thank the German for that... For the first part of that important war... The US was busy making money by selling armement to europe. WWII was anything but peaceful. And as Sun Tsu said ...It's better to fight a war as far away as possible from your own home...So my guess and opinion on this is ...It seem like it was peaceful...But not realy indirectly,. If you follow my logic.

@RemiDallaire: Absolutely! It was certainly not a time of peace. I was referring to the hand off of the Title. They were the last undisputed worldwide Supreme (no one could go up against them and have a hope to win) until about the time of WWI. I believe they began to see the US and Germany were overtaking them WRT military might and industrialization. It wasn't long before they began dismantling their own power positions themselves on purpose. They stopped accruing foreign territories (not immediately after WWI, but not long afterward) and began to divest themselves of claims of Supremacy before Germany (and Axis powers) rose up to try to take the title of World Supreme Power. Much of our wealth came from Great Britain and the allies ceding their sole power of military defense to a certain extent, by empowering the US to defend them through strategic alliances and financial dealings that favored the US. This was in response to the growing menace of the USSR, as I understand it. This was the beginning of the Cold War with its arms race.

It wasn't until the end of the Cold War that much of Europe no longer saw the need for an Allied Superpower for defense against the USSR. But by that point, we had moved from Superpower status to become a true Supreme power. (i.e. nobody had the ability to challenge the US without a committed coalition). When we suddenly had no foe powerful enough to restrain us, many of our European allies suddenly stopped seeing us as a protective shield against an existential threat and started seeing us as a potential existential threat due to our excessive power.

Even this did not turn our friend and ally (Great Britain) against us and lead them to try to wrest power from us. They were content to support our leadership while cautioning us against the dangers/risks of hegemony. We've had our ups and downs, but we remain strong allies.