The United States declared war against the government of Germany, not "Nazis." It's in the declaration, twice:
JOINT RESOLUTION Declaring That a State of War Exists Between The Government of Germany and the Government and the People of the United States and Making Provisions To Prosecute The Same
... the President is hereby authorized and directed to employ the entire naval and military forces of the United States and the resources of the Government to carry on war against the Government of Germany
The responsibility for starting World War II falls squarely on Germany, not some udnefined group of national socialists.
JOINT RESOLUTION Declaring That a State of War Exists Between The Government of Germany and the Government and the People of the United States and Making Provisions To Prosecute The Same
... the President is hereby authorized and directed to employ the entire naval and military forces of the United States and the resources of the Government to carry on war against the Government of Germany
The responsibility for starting World War II falls squarely on Germany, not some udnefined group of national socialists.