Papers!
As a life long New Englander, I can put some minds to rest on the question of America's DoW against the British Empire. Granted there was "childishness" in America's political thinking at the time. Not to mention arrogance. But was there any less arrogance, or indeed not far more in the halls of the Admiralty? IIRC, the British government didn't enjoy the complete command/control over the senior service that it does today. If the Admiralty wanted to impress American seamen, they did, without consequence. Often, the impressed seamen were hanged as disciplinary examples to the British crews. After all, it's not like the captains had to worry about angry families waiting for them with pitchforks and torches in Southampton over executing Americans.
By the time of the start of the War of 1812, more Americans were in the Royal Navy than in the US Navy. I don't recall the exact numbers, but it was between 1100 and 1200 men! When presented with complaints from the US State Department, the British Government would always defer to the Admiralty. The Admiralty, in without a doubt the most galling of statements one could imagine, would reply that the men in question, having no proper documents to prove their nationality, would not be released. This announcement, used repeatedly, could not be designed better to infuriate the US populace, since every American seaman had been carrying such documents to sea for many years (for obvious reasons). When the documents were produced, the British captains would simply destroy them.
It was impressment, and only impressment, that united the American people over the war. Yes, those who had designs on the west or Canada WERE engaged in very childish imperialism. And it was they who sparked the fire. But it was the limitless arrogance of a Royal Navy, apparently beyond the control of its' own government(?), that provided the fuel for that fire.