Before pearl harbor, what u. s. policies suggested that the united states would join the allies?

Despite remaining neutral for  the two first years of the war, several policies and action by the Roosevelt administration implied the USA would eventually join the allies.

The usa supplied military equipments to China,Britain and the soviets through the lend-lease act of 1941.
The pacific theatres resulted in sporadic combatant activities as well as sanctions against Japan, to decrease its aggression.