What caused the US to shift from isolationist to interventionists?

In the early 1940s, US policies such as the Cash and Carry Program and the Lend-Lease Act provided assistance to the Allied Powers in their fight against Germany. This growing involvement by the US marked a move away from isolationist tendencies towards interventionism.

president thomas jefferson commissioned the expedition shortly after the louisiana purchase in 1803 to explore and to map the newly acquired territory, to find a practical route across the western half of the continent, and to establish an american presence in this territory before britain and other european powers

e. all of em

~courtney