Why?
In studying the War of 1812 last year, one fact I had forgotten was that between 4,000 and 10,000 American sailors had been impressed into service on British vessels. If that is not justification for war, I do not know what is.
The major factor leading to the American declaration of war was probably the desire of westerners (War Hawks) to annex Canada, which they proclaimed would be, "merely a matter of marching." LOL
The war was admittedly probably "necessary" in the sense that it taught the Brits to stop thinking of USA as a semi-colony not deserving the respect of the "real" nation.
OTOH, there was something shameful in our attempt to stab the British in the back when they were the main factor keeping the world's worst dictator before Hitler contained.
Our performance in the War was an astonishing mishmash, with the most abject and humiliating possible defeats alternating with sublime courage and valor. Bladensburg and New Orleans. Detroit and Constitution/Guerriere.