Kalvan Kingmaker

The Kalvan series is a series of science fiction novels started by H. Beam Piper and continued by his authority John F. Carr, about a Pennsylvania police officer who is transported to an alternate world. The series is part of Piper's Paratime series and features many of the characters from that series. The police officer, Calvin Morrison, is picked up by a "cross-time flying saucer" and dropped off in an alternate Pennsylvania where "Aryans" migrated east across Asia and the Pacific Ocean and arrived in North America. This is different from the real world, where they moved west into Europe.