https://en.wikipedia.org/wiki/United_States_military_casualties_of_war https://en.wikipedia.org/wiki/United_States_military_casualt... World War I - 116,516

https://en.wikipedia.org/wiki/United_States_military_casualties_of_war https://en.wikipedia.org/wiki/United_States_military_casualt... World War I - 116,516 World War II - 405,399 This was only military deaths, at the time no major bombing of US cities occurred, the closest was the ships destroyed in Pearl Harbor. There are no guarantees that Russia wouldn't start bombing US cities in an all out war, in fact it is quite likely. There is also no telling what China would do. If China were to become involved and join the Russian side after a lengthy battle between the US and Russia, it would essentially play the role that the US did in world war 1 and 2. There are heavy costs for engaging in a war with an advanced military.