[Belegorn]

There is no way Sauron could take his fight to Aman and hope to succeed. The Númenórean host his armies could not stand against barely set foot on Aman before they were dealt with. Only Melkor at the peak of his powers could hope to accomplish such a thing, as once upon a time he competed with them all.

Had Sauron reclaimed the One the Elves would be between a rock and a hard place because all their work with the Three would be laid bare. The West is Elven-home. All other species would still be there. Unfortunately for Men, the Dúnedain are few and are not much of a threat as they were in the 2nd Age. Not only that, Sauron has Dúnedain in his armies. They did not just breed out ruling over lesser men as the sons and grandsons of Castamir did.

Some people might give up, other might not. Guerilla warfare would perhaps ensue sort of like the Rangers of the North did with Orcs and other threats to Eriador. I also am not sure if Galadriel would turn tail. She seems to be the one to have been there to fight to long fight against Sauron and I'd think she'd be there.