The military ground unit is a random mixture of Heer (regular army) and Waffen SS (what would now be called "special forces"). In reality, the Luftwaffe had its own ground forces, and it would have been them instead.
The rocket launcher is a "Panzerschreck". This is an anti-tank weapon firing a shaped charge designed to punch a hole in armour and would not generate the enormous anti-personnel explosions depicted.
The B-25 attacks the B-17 by dropping bombs on it from a little above. They explode and destroy the B-17. In reality, bombs have to fall a considerable distance - several thousand feet - before they are armed and capable of exploding. This is to avoid just the situation depicted as in a bombing raid with many bombers attacking, it is possible for one aircraft to be hit by bombs dropped by another and in such circumstance, you would not want the bombs to be armed.
Colonel Krieger carries a Hitlerjugend (Hitler youth) dagger. He should have a SS dagger.
The B-17 could not have carried a nuclear weapon. The only allied aircraft capable of carrying a nuclear weapon in 1944 was the RAF's Avro Lancaster - which could carry up to 10 tons of bombs in a large, contiguous, bomb bay. The B-17 had a small bomb load, not much greater than some fighter-bombers, and a very small bomb bay, and was incapable of delivering a 1940s-era nuclear weapon due to it's size and weight. Even the B-29, which ultimately dropped the two allied nuclear weapons, could not carry an atom bomb in its standard configuration of two small bomb bays, and the special nuclear armed version had to have Avro Lancaster bomb bay components fitted. And, the modified B-29s did not fly until Feb 1945. After this film is set.
The B-17 seen at the beginning of the film bears the tail number 485829. This aircraft is owned by The Yankee Air Museum and is based at the Willow Run Airport in Michigan. Her name is "Yankee Lady", and she is a 1945 B-17G and was delivered to the USAAF in July of 1945. Since this film takes place in 1944 it would be impossible for that particular aircraft to be in the air at that time.
The Me-262 has modern (red) gas turbine intake covers.
Towards the 20-30 minute mark, there is a scene where a single green double prop plane flies by the one American and one German pilots in the woods fighting each other, in that fly by, you can see the Drones shadow in the ground while flying over said plane.