"Dome Around America" by Jack Williamson

Dome Around America is set a couple hundred years in the future. The United States is enclosed in a force field which has preserved its air and water from the disaster caused by a "dwarf star" wandering through the solar system. The US offered this technology to the rest of the world, but Cold War tensions caused the other countries to refuse it, and to disbelieve US reports of the dwarf star danger. (There was also that accident in Australia, but that was probably commie sabotage anyway!) I'm guessing that one of the changes from 1941 to 1955 was substituting Soviet villains for Nazi villains. The dwarf star sucked away the atmosphere from the rest of the Earth, and it is assumed that it is all a moon-like desolation, just as it looks.

Barry Thane is a young man, part of the "Ring Guard", the dwindling crew of men who guard the dome from sabotage. But he has come to believe that something weird -- aliens, maybe? -- live Outside. So he is mentally prepared when he notices a moving rock penetrating the dome, and what he discovers is a camouflaged spaceship/ground vehicle, sent by an organization of surviving humans who are consumed with hate for America, and who live in domes with limited water and air on the former ocean bed. Barry foils the plot of the man in the invading ship, Glenn Clayton, and he hatches a plan to impersonate Clayton and infiltrate the Outside. But Clayton has plans of his own ... And both men are vulnerable to the charms of a woman of their enemies ...

It's really silly stuff, with not much in the way of redeeming values. The science is nonsensical. The resolution is just plain wholly unbelievable. The story itself moves nicely enough -- Williamson was too much the pro to fail to tell a solid story scene by scene. But all in all it is a fairly prime example of why routine 1940s SF is so often unmemorable. (Strange At Ectaban)