U.S.A. vs The World. no nukes

[DanielX]

The US will lose in a long, drawn-out, to-the-death war - not enough resources to face everybody else - but would put up one  hell of a fight.

The US has essentially overwhelming naval superiority (the US has more aircraft carriers than the rest of the world combined, for example,), which will help keep the huge numbers of Eurasian troops away from the US mainland for a little while, leaving the US army facing only Canada and Latin America, which the US might be able to take on (although it won't be easy).

In the long term, though, the US will be cut off of most of the world's resources, except for conquered areas - which may face insurgency problems (Mexico will be a bloody mess, as its one place that the US could relatively easily conquer and yet have a very large, rebellious population...). Mass production of aircraft and submarines from other powers will eventually, over the course of several years, overwhelm US naval and air defenses, and then the millions of Eurasian troops can invade.