Final answer:
Colonists were upset with the Proclamation Line of 1763 as it impeded their westward expansion and violated what they felt was their right to settle on lands won after the Seven Years' War, escalating tensions that led to the Revolutionary War.
Step-by-step explanation:
The American colonists were upset with the British Proclamation Line of 1763 because it restricted their movement and aspirations for expansion. After the Seven Years' War, the British government issued the Proclamation to prevent further conflicts on the frontier, particularly with Native American tribes and the remaining French presence. They sought to avoid the costs of defending new territories, which were considered Indian Reserve lands.
However, colonists saw the Proclamation Line not as a protective measure but as another example of tyrannical overreach. They had expected to move west and were frustrated by the British Crown's seeming indifference to their entitlement to land, especially given the land grants some had already received.
This restriction directly countered the hopes for westward expansion, exacerbated resentment against British policies, and contributed to growing tensions that eventually led to the American Revolutionary War.