This is very US specific.
Canada, Australia and New Zealand , among others, declared war very soon after Britain did. They poured people and supplies into the war effort.
My FIL was in the Canadian Air Force. My father tried to enlist 3 times, but was refused because he was in an essential civilian occupation. He was on the first convoy into the Mediterranean, the ship next to his was hit and limped to Tripoli. It could have been his ship.
Gentile Danes saved 90% of Jewish Danes when Germany decided to round them up.
Lots of inspiring actions before and during WWII.