The US never had a full war on their home territory in recent history (even including both world wars).
The closest anyone's been able to point out to me are Pearl Harbor (which -- though striking -- was just a single attack) and some practically uninhabited islands Japan took over for a while.
The last time foreign soldiers invaded the US proper was when Canada marched into Washington.
German UBoats operated with near impunity up and down the East Coast as well as in the Caribbean. Many indigenous tribes that fell under the purview of the US suffered under Japanese attacks and incursions in the Aleutians. I find that many Europeans wish to posses the World Wars above others. Though the governments in Europe share the largest responsibility for starting the War (I) and allowing the War (II), and they also have the most collective casualties, suffering is suffering regardless of degree.
Side note: a few Canadians marched into Washington with their British overlords. I have never understood why Canadians always seem to reference 1812 and never mention Dieppe when they talk about Hosers on the warpath.
Suffering is suffering, but there is still a huge difference between having U Boats off the coast, and having entire cities flattened and thousands of civilians killed, which was the case in most of Europe and south east Asia. It also meant that as the war ended, the US was the only one of the belligerents that wasn't effectively bankrupt, but was on the contrary booming.
There's one hell of a difference between having submarines patrol your coast lines and having soldiers on your ground and bombers in your skies. There are worlds between having soldiers die and having civilians die, en masse. You're talking about indigenous tribes. I'm talking about people the man in the (US) street would recognize as "American" (yes, it's discriminatory, but such is society).
Sure, war is hell. But a war at home is an entirely different category of horror than a war overseas or off the coast. Its effects on the collective psyche are entirely different.
Interestingly, none of them on their home territory.