Sarah says the bomb in the basement is a 2,000 lb Type 80. The plans given to Frank are of a Type 98 No.25 which weighs just 532 lb.
In 1947 John Smith was awarded the Knight's Cross, however to qualify for the Knight's Cross, a soldier had to already hold the 1939 Iron Cross First Class. John Smith was with a US Intelligence Office in the Pacific during WWII.
Trade Minister Tagomi is seen and heard bowing to his ancestor (butsudan) in his shoes. Japanese would have kept the removal of shoes inside their home as a key icon of their attention to keeping the inner home clean. Even without a proper porch/genkan he would have either had one created or created a barrier to keep his shoes when entering. This would especially be true when kneeling.
Frank says the bomb casing is 5 centimeters (about 2 inches) thick, but Type 98 No.25 shown on the plan had a casing only half an inch thick. It also used Type 98 (Hexanite) explosive, not picric acid as stated.
There was no 2,000 lb "Type 80" land bomb used by the Japanese. The No. 80 Land Bomb was 1,760 lb.
The world map in Obergruppenführer's office shows Brasilia as the capital of what remains of Brazil. Planning and construction of Brazil's new capital did not begin until 1956. Doubtful this would have taken place given the outcome of the war and the partition of Brazil in this time-line. There would have been no Brasilia and the capital would have remained Rio de Janeiro.