"I doubt any axis troops could actually stage a land invasion of N America. "
ah really?? 'Murican pride ^^ Then you should read this:
Giuseppe Zangara's assassination of U.S. President Franklin D. Roosevelt in 1934 led to the weak governments of John Nance Garner (formerly FDR's Vice President), and subsequently of Republican John W. Bricker in 1941. Both politicians failed to lead the country to recovery from the Great Depression and also maintained the country's isolationist policy against participating in the Second World War; thus, the U.S. had insufficient military capabilities to assist the United Kingdom and the Soviet Union against Nazi Germany, or to defend itself against Japan in the Pacific.
In 1941, the Nazis conquered the USSR and then exterminated most of its Slavic peoples; the few whom they allowed to live were confined to reservations. In the Pacific, the Japanese destroyed the entire U.S. Navy fleet in a decisive, definitive attack on Pearl Harbor; thereafter, the superior Japanese military conquered Hawaii, Australia, New Zealand and Oceania during the early 1940s. Afterward, the Axis Powers, attacking from opposite coasts, conquered the coastal United States and, by 1947, the United States and other remaining Allied forces had all surrendered to the Axis.
Japan established the puppet Pacific States of America out of Alaska, California, Hawaii, Oregon, parts of Nevada and Washington as part of the Greater East Asian Co-Prosperity Sphere. The remaining Mountain, Great Plains and Southwestern states became the Rocky Mountain States, a buffer between the PSA and the remaining USA, now a Nazi puppet state in the style of Vichy France. Having defeated the Allies of World War II, the Third Reich and Imperial Japan became the resultant superpowers of the world and consequently embarked upon a Cold War.
One of the core narrative elements, (Operation Dandelion), is centered on a preemptive Nazi nuclear strike on the Japanese Home Islands. The Nazis "have the hydrogen bomb" and the ability to wipe out the Home Islands. Their nuclear energy capabilities also fuel extremely fast air travel and the colonization of the moon, Venus, and Mars.
After Adolf Hitler's syphilitic incapacitation, Martin Bormann, as Nazi Party Chancellor, assumes power as Führer of Germany. Bormann proceeds to create a colonial empire to increase Germany's Lebensraum by using technology to drain the Mediterranean Sea and convert it into farmland (see Atlantropa), while Arthur Seyss-Inquart also oversees the colonization of Africa and extermination of most of its inhabitants. Meanwhile, the Reich sends spaceships to colonize Mars and other parts of the Solar System.
Soon after the novel begins, Führer Bormann dies, initiating an internal power struggle between Joseph Goebbels, Reinhard Heydrich, Hermann Göring, and other top Nazis to succeed him as Reichskanzler.
A Riddley Scott's adaptation of this novel is to be released soon!
http://www.telegraph.co.uk/culture/tvandradio/tv-and-radio-reviews/11347173/The-Man-in-the-High-Castle-Amazon-pilot-review-stylised-and-stylish.html:)