Which factor directly contributed to the us decision to declare war on britain in 1812?

There were actually several reasons why the war of 1812 started. The official reason as made clear in the declaration of war by the United States of America to Great Britain was the Impression Issue that was made by the British Government under their Orders-in-Council.  This Impression Issue is an act whereby men are forced by the government for induction into military service.

The War of 1812 was declared by the United States Congress to Britain on June 18 of that year, highlighting some conflicts that were not resolved by the war of independence, which took place two decades earlier.

Some of the causes were: Trade restrictions imposed during the war in Great Britain and France, dominated by Napoleon Bonaparte; the imprisonment of US merchant sailors at the hands of the British Navy, and the alliances of the British with indigenous tribes during the expansion of the Americans through indigenous territories and into Canada.

i'm not sure i understand what you are trying to ask, if you give more information, that would be most .