Think about it
They didn't. Germany declared war on the US on 11 December 1941
Germany didn't really attack US, US entered war because of Japan, and when the allies of US were attacked then US joined. The US was fighting 2 wars, 1. Japan 2. Germany
The US did not declare war on Germany. Germany declared war on the US shortly after the Japanese attack on Hawaii.
Germany did NOT want to fight the US. The US needed a cause (reason) to declare war on Germany. Germany was NOT going to enrage the US. The ONLY reason Germany declared war on the US on December 11, 1941 was because Germany was hoping that Japan would reciprocate the favor and attack the USSR (Russia). Germany helps Japan; Japan helps Germany...TRIPARTITE PACT.
The US did not declare war on Germany in 1941, Germany declared war on the US as a measure of solidarity with Japan after their attack on Pearl Harbor and the Philippines.
After the Japanese attack on Pearl Harbor and the US Decleration of War against Japan, Germany declared War on the US.
The Zimmerman Telegram.
Germany declared war on the US on 11 December 1941, four days after the Japanese attack on Pearl Harbour.
The attack on the US by Japan in Hawaii. The next day, Germany declared war on the US. Game on.
calais
The US did enter into an undeclared shooting war with Germany in the fall of 1941 because Germany has declared war on the US.
Relations between the US and Germany were very strained as a result of the German policy of unstrestricted submarine warfare. In 1915 the sinking of the Lusitania played a key role in turning opinion in the US against Germany. In 1916 an attack on the Sussex resulted in Germany giving a solemn pledge not to attack pssanger vessels. However, a year later, Germany revoked this pledge. There was also the Zimmermann telegram.