Final answer:
The main cause of the War of 1812 was the impressment of US sailors by the British and their support of Native American resistance.
Step-by-step explanation:
The main cause of the War of 1812 was the impressment of US sailors by the British, along with their support of Native American resistance.
Impressment refers to the British practice of seizing American sailors and forcing them to serve in the British navy, which violated American sovereignty and caused outrage among the American people.
In addition, the British supplied arms to Native American fighters, who were resisting further US expansion in the Great Lakes region.
Overall, these actions by the British led to strident calls for war against Great Britain, which eventually led to the War of 1812.