What actions did the U.S. take before going to war with the Axis Powers?

I assume that you are asking about actions that were not exactly
neutral but which fell short of actual acts of war. If so, the major things that the US did
included:

• The destroyers for bases deal that FDR made
  with Britain. This gave Britain ships and it freed up British forces (from the bases) to go and
  fight.


• Lend-Lease. While still maintaining neutrality, the US sent
  huge amounts of war materiel to the British and the
  Soviets.


• Having the US Navy protect convoys of ships (both
  American and British) going from the US to Britain.

All
of these actions were clearly intended to help the Allies win the war even though the US was
still officially a neutral power.