If the United States enters the European war in 1939

How does the European war change if the United States enters in 1939?

German surface raiders face a much larger Allied naval net, while early American troops and aircraft greatly strengthen France, Britain and Norway.

The United States Atlantic Fleet would probably combine with the Home Fleet while American cruisers joined British and French groups hunting raiders. Deutschland and other German surface ships would face many more patrols across the Atlantic. American troops and aircraft would also begin crossing early enough to reinforce France, Britain and perhaps Norway. That would turn 1939 into a resource problem Germany was poorly prepared to solve and could even alter Soviet calculations in 1940.