Why did Americans believe the British supposed Tecumseh?

Many Americans believed that the British were supporting Tecumseh, the Shawnee leader, because of the growing tensions between American settlers and Native American tribes in the Northwest Territory. Tecumseh had sought to unify various tribes to resist American expansion, and his alliance with the British during the War of 1812 fueled suspicions. Additionally, the British were seen as a potential ally for Native Americans in their efforts to protect their lands from American encroachment. This belief contributed to American hostility towards both Tecumseh and British forces during the conflict.