You probably have already heard the basic buzz around this show but the premise is this: That WWI was won by the Axis powers when the Germans developed the Atom bomb first, dropping it on Washington DC, which naturally obliterated all central government along with most of the military structure. Of course, most the armed command WAS in fact in Europe (England) at the time, and it begs the question of whether Ike and Gen. Patton would just fold up. Probably, if it were made clear that NYC and a few other big cities were next if we didn't surrender. The US is then divided up basically as everything west of the Rockies is Japanese, and everything East is German. There is some resistance still happening, but it definitely underground, and not active in large scale. One can rightly assume that any energetic or talented military units in Europe at the time were neutralized one way or the other.
In any case, regardless of whether or not any such thing WOULD have been feasible, that is the premise and it certainly doesn't seem impossible when one looks at the ups and downs of history. What makes it so great is that the Production values of the series is way up there with the very best period piece cinema I've ever seen. The amount of detail has clearly been thought out to the nth degree, which seeing how as Ridley Scott is the executive producer, this is not surprising. Amazon must have spent an insane amount of money even in terms of location scouting to bring this thing to life.
The viewer is dropped right into the action immediately in the first episode, and they do not spoon feed you all the Hows, Whats and Whys of the storyline. There is a mystery that is revealed early on and it motivates all the central characters, both the reluctant heroes, the on-the-fence people just trying to get by, and the dedicated villains too. Speaking of which, the series wisely does not allow the "bad guys" to devolve into mere caricatures, though on occasion the line is pushed. The show also do not go too heavy-handed with Japanese/Nazi iconography. No question that things are fundamentally different in this reality, and the cultural aspects of the two countries on their American territories play out in ways both large and also subtle. However, many aspects are probably not much different than being a conservative 1950s, though it's also clear that the US doesn't quite have the booming economy it did in history
They have a great cast throughout, most importantly with Alexa Davalos as Juliana Crain, who is probably the most sympathetic of all the various personalities. But really, the whole cast gets some very meaty roles to work with and all come through. This especially is the case with some of the well-known Japanese actors (like Cary-Hiroyuki Tagawa) brought in to fill out some of the key roles of the Pacific States.
Future Seasons have plenty to work with and I for one can't wait to see them. Unaddressed areas that seem oddly absent are: Britain's role in the world, nor USSR or China's, both the arch enemies of Japan and Germany. One assumes that maybe once the A-Bomb was used on DC, London and Moscow were probably next in very short order. Still, I am hoping that some expansion of the world is dealt with over time.