none of the two worldwars took place on US soil, and the US entered both conflicts relatively late, so there is less US cultural knowledge about them (mostly in the form of “relative X went overseas and died/came back traumatized”). but in europe, the countries were the place the WWs were happening. and they experienced a different way how those conflicts came to play: countries interfering in the affairs of other countries.
this is more clear in the context of WWI: an austrian is shot in serbia, because serbia wants independence, but russia intervenes because it wants to control serbia, and germany & austria fight russia, and france has an alliance with russia, and germany always wanted to fight france anyway, ……… the level of intervention and trying to intervene in other countries' affairs leads to a chain reaction that brings about calamity.
additionally, some countries (*cough cough*) had some, let's say, embarassing behavior in the world wars