I mean even discarding that. Hypothetically, let's say the US and China declare war on each other. Neither country would be able to invade the other. I mean, the US is good at force projection, but how in the world would any nation conduct an amphibious invasion of a country like China and manage supply lines across the Pacific sufficient to support an invasion force?
The US could definitely do that, their logistics capabilities are immense. On top of that you have the submarine fleet, as well as assistance from regional allies. Probably not enough to take the entire country, but enough for it to capitulate through conventional means.