It’s going to take a little more than your best lapsang to fix that, Arthur.
War of 1812, not the American Revolution. Matthew's uniform is based on that of the Canadian Regiment of Fencible Infantry, which was designed for Lower Canada. Nope, many were not thrilled to wear the red coat. I don't remember what Arthur's is, only that it was worn for battles in Europe, and that it outranked Matthew's.
In Hetalia terms, within 50 years Matthew 1. Is ceded to Britain (1763) 2. Gets invaded by his brother (1775) 3. Gets to see his papa have a complete massacre of a breakdown (1789) 4. Gets invaded by his brother AGAIN, and gets his capital burned down (1813). He's been having a couple rough years.