Final answer:
Southeastern tribes primarily supported the British during the American Revolution, mainly to protect their lands from American expansion, although some tribes in New England sided with the American Patriots.
Step-by-step explanation:
During the American Revolution, the southeastern tribes predominantly supported the British. Although some native groups, including the Iroquois Confederacy, initially declared neutrality, this stance did not hold uniformly. The decision by many tribes to abandon neutrality and side with the British was largely influenced by attempts to protect their lands against American expansion.
On the other hand, support for the American Patriots was less common but did exist to a greater extent in New England, where closer relationships with colonial neighbors were established. The Proclamation Line of 1763, supported by the British, offered a temporary sense of security against encroachment, swaying many tribes to side with the British in hopes of upholding this boundary.