Operation Downfall was a proposed Military invasion of the Home Islands of Japan by the United States, with limited help from Britain. It's hard to determine exactly how many casualties were expected, but 500,000 Purple Hearts (US medals given to every wounded/dead soldier) medals were produced for the occasion. Estimates ranged from about 500,000 to 1 million casualties on the US side. Yet in the 65 years following the end of WW2, the US military STILL had not suffered 500,000 casualties overall, despite the Korean and Vietnam Wars. Considering public support for the Vietnam War in the US was a serious, ongoing issue, I would imagine the US public wouldn't support 500k casualties just because of Pearl Harbor.

Despite this, I have never heard a word uttered anywhere about the US Public not supporting the campaign. Every documentary, every book and every class in school has presented it as a given that Americans considered it a 'necessary sacrifice'. I have heard that the US considered blockading the Home Islands indefinitely to get Japan to surrender, but they didn't because "it would take too long and the public would lose patience". What am I missing here? Why did Americans have 0 problem with Operation Downfall and made a giant fuss about Vietnam?