What four items the united states supplied the allies with were:

manpower
food
a boost in morale
submarines
military equipment

The four items the United States supplied the Allies with were:

1. Manpower

2. Food

3. Boost in morale

4. Military equipment.

"During World War II, the United States began to provide significant military supplies and other assistance to the Allies in September 1940, even though the United States did not enter the war until December 1941. Much of this aid flowed to the United Kingdom and other nations already at war with Germany and Japan through an innovative program known as Lend-Lease."