Tom, a while ago, (and just a few minutes ago conveniently) I suggested a war in this time period with a different POD. I'll tell you what I told Norman, because your posts are similar.
I think if you'd like to have a GB vs US war in late 1830s to the early 1840s, the Caroline Affair is a better POD because the US and GB came closer to war than they did in 1837. The old post is, unsuprisingly, called "The Caroline Affair." Here's some info on it from Encarta:
"Caroline (vessel), privately owned American ship seized and destroyed by Canadian troops on the American side of the Niagara River off Grand Island, New York, on December 29, 1837. The incident, in which one American was killed, occurred during a rebellion in Upper Canada (now Ontario Province) and threatened to cause war between the United States and Britain (at the time, Canada was a British colony). The steamer had been used by American sympathizers to carry supplies to a party of Canadian rebels on Navy Island, above Niagara Falls. In 1840 Britain asserted that the destruction of the Caroline was a legitimate act of war. The U.S., however, repeatedly demanded redress on the grounds that the Canadians had invaded U.S. territory in time of peace. The matter came to a crisis during the same year when a Canadian deputy sheriff visiting the U.S. boasted of participating in the affair and was tried for murder in a New York State court. In spite of the demand of the British ministry for his release, the trial continued; war between the two nations was prevented only by his acquittal. Peaceful relations between Britain and the U.S. were finally restored in 1842 with the signing of the Webster-Ashburton Treaty, in which Great Britain expressed regret for failing to make an immediate apology for the Caroline affair."
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