What if Hitler launched unrestricted submarine warfare across the Atlantic attacking all potential Britain bound merchantmen worth a torpedo in their sites from July 1940. IE, this means rules of engagement as loose as those adopted in December 1941 after declaring war on the US. Only he doesn't declare war, just justifies it as part of the war forced on him by Britain, or maybe just doing it and not acknowledging it.
How does the U.S. react?
a) Declaring war on Germany as soon as the pattern becomes apparent, committing to alliance with Britain and assuming US air, naval and ground forces will be employed against Germany as they become available. So basically US declares war within six weeks.
b) Beginning undeclared naval war against U-Boats, and aiding Britain, but not declaring war or working to engage air or ground forces any earlier than OTL.
c) US doesn't do anything other than coastal and near shore defense for several months, before any consensus is reached for further steps.
Hitler does it because he thinks unrestricted warfare is the reliable way to get Britain, and with France fallen, there's no place for an American Army to land.
How does the U.S. react?
a) Declaring war on Germany as soon as the pattern becomes apparent, committing to alliance with Britain and assuming US air, naval and ground forces will be employed against Germany as they become available. So basically US declares war within six weeks.
b) Beginning undeclared naval war against U-Boats, and aiding Britain, but not declaring war or working to engage air or ground forces any earlier than OTL.
c) US doesn't do anything other than coastal and near shore defense for several months, before any consensus is reached for further steps.
Hitler does it because he thinks unrestricted warfare is the reliable way to get Britain, and with France fallen, there's no place for an American Army to land.