Other than the Civil War, the US has never really had war on its on soil, however Europe has, many who lived through WWII are either very old or have already passed away. Europe has war in Ukraine but had conflict in the Balkans within living memory (early 90s)
So other than 9/11, the US has never really had mass casualties on home soil ( mass shootings aside ) but the US and the west just inflict this on others, either directly or by supplying weapons, not sure if we can call Israel (under recent regimes) as a proxy to the US, in a similar way we call Hezbola or Hamas proxies to the US.