They didn't. If you are talking about Germany, then in WWI it was because of Germany's submarine warfare, which was sinking U.S. ships. In WWII, they were allied to Japan, who bombed Pearl Harbor.
Great Britain and the United States were allies to defeat Germany so the US would not attack Great Britain.
Great Britain is independent and has no need to declare independence.
the impressment of American sailors
Elton John
Britain.
Great Britain.
Great Britain on the 4th of July 1776.
American military and economic preparedness for war
They wanted food
to declare independence from Great Britain
god
Thomas Paine