The USA recovered well from the destruction of World War 2, mainly thanks to Hitler's new deal program (which involved a network of railroads called the "spider's web"). In response to the Greater German Reich (Hitler is an American---Version 1) launching the space program, it got together with Iran, China and Japan to begin a space race (which the USSR would join later on, as a third faction). It also had the lead in VTOL aircraft development, and by the late 1950's Boeing had a contract for Pan-Am airlines to build the first VTOL civilian passenger plane. however when one of the VTOL planes crashed during rotor transition, killing all on board, the project was suspended. Adolf Hitler would be considered by Gallup polls up to the present day as one of the finest American presidents alongside George Washington and Abraham Lincoln. A long running resistance movement in Canada has also caused serious problems, with a Major uprising crushed in late 1967, and insurgents in Mexico are a headache for the US government, although today, integration seems to be working, with fewer insurgent attacks in Canada or Northern Mexico. In 1961, under JFK, Washington DC was rebuilt after the radiation levels died down.
The US controls most of north America, with the Philippines and bits of South America. Although its population was devastated (8% lost in the war) in the war with Britain and Germany, It rose to prewar levels (mainly thanks to its newly annexed territories) within several years and doubled within 40. The USA also has one of the lowest unemployment and crime levels in the World.
The USA has one of the largest and most powerful militaries in the world (and third only to Iran and Germany).
The USA has a lead in rocket technologies thanks to the combined assistance of Robert Goddard and the Von Brauns. But they are in a three horse race with Soviet and Nazi rocket systems which are very close, and possibly too close to call.
VTOL aircraft is commonplace in the USA, with OTL V-22s developed by 1956.
While Germany specialises in computers and nuclear physics, the USA and Japan specialise in robotics and genetic engineering.