The physicist who views Juliana's film in the camp outside Denver refers to the danger of an explosion as equivalent to a small atomic bomb. Although the term "atomic bomb" was coined by H.G. Wells in 1910, it did not enter into popular culture until after the bombings of Hiroshima and Nagasaki in 1945. In the alt-history where Germany developed nuclear weapons first it is called a "Heisenberg device" after Werner Heisenberg.
The amount of molten metal in the crucible does not change as it is being poured to cast the giant swastika.
As the Liberty Bell is being hoisted into the melting pot and there is an under view of the bell chamber, it can be seen that the famous crack, and the bolt repair, are missing. Since the bell predates the Nazi invasion, it should have the crack.
When Wyatt and Julianna pass through the Nazi border in Colorado between the Neutral Zone and the American Reich, we see tree-covered mountains. However, eastern Colorado is in fact flat and dry.