Nazi Germany was never gonna beat the Soviets fighting the US and Great Britain also at the same time, not unless Japan could have moved their military to Europe and helped them out.
Insurgency and guerilla campaigns are a different story because nobody can really win those unless you wanna go scorched earth and nobody really wants to do that, but in recent history everytime we fight an actual conventional military the US damn near wipes them off the face of the earth. We beat the shyt out of the Japanese, we killed MILLIONS of Koreans and hundreds of thousands of Chinese, the US fukked up the North Vietnamese Army so bad they had to resort to using farmers to fight their war for them eventually... and the US never had any boots in the ground in North Vietnam ever and we almost completely wiped them out. Iraq was the 4th most powerful military in the world at the time of Desert Storm and you see how that worked out for them, they didn't even last a month.