Western americans clamored for war because they believed that

In 1811 Western Americans waged for war because of the belief that the British agents in the West had stirred up the Indian unrest to block America's expansion.
On 4th November 1811 President James Madison called Congress to an early session to report Britains "hostile inflexibility" and its continued "trambling on rights which no independent nation can relinquish."
After Britains refusal to revise its policies, Madison asked Congress to declare ar citing Britains history of abuses against the U.S between 1803 and 1812 and were over six thousand. They comprised of violation of neutral trade and incitement of the Indians to wage war on the western frontier.