I have decided that, in the spirit of Diversity, Equity and Inclusion, I shall no longer focus on giving favor to what I consider the strictly "American cartridges." I shall now commence celebrating the 7.65x17mm, the 6.5 x 55mm, the 7x57mm Mauser, the 9.3x74R and some of the other greats (sorry, I can't do the 8x22mm Nambu)...
Just kidding. Under the power vested in me by the internet, I'm gonna decree the .45 ACP as the American cartridge of all time. Why was not John Moses Browning sainted by the Holy Roman Catholic Church? Oh, wait... he was a Mormon.
Seriously, though guys -- after due consideration, I have come to the conclusion there is no single "most American of all rounds." Our country has birthed some of the most impactful, effective firearms cartridges/calibers in history, so to proclaim any one of the greats as "the most American" kind of slights those you think didn't quite measure up. I mean, really, .22LR, .38 SPL, .357 Magnum, .44 SPL, .44 Magnum, .45 Colt, .45 ACP, .30-30 Winchester, .308 Winchester, .30-06 Springfield, .45-70 Government. .257 Roberts, .270 Winchester, 7mm Remington... How can you say that any one is more culturally and historically significant than another, more deserving to be called the American round?