Why did conflict on the american frontier increase tensions between the united states and british

This is really a question on Alliances and Territory.

Historical Background:

The British was able to create fairly complex alliances with many of the Indian tribes surrounding the newly created U.S. With the alliance, they were allowed to trade with the Indians and set up forts, in return of supplying the Indians with equipment such as muskets.

Conflict:

Conflict aroused even before the expansion west and the American-Indian Wars. Indian alliances were extensive within the European countries, and they were used by both French and British during the French and Indian War. During the expansion west-ward, many Indian tribes turned towards the British for support in defending their lands. Britain essentially supplied many of the Indian tribes, resulting in large conflicts. Because of these supplies, Britain-US relations started to worsen. This soon led to another full-scale war with Britain, and numerous military-operations against the Western tribes.

~Rise Above the Ordinary