OK, sorry, right about the War of 1812, should have said 20th century onward.
Arguably, the most important battle in American history, outside the War of Independence and Civil War, was the Battle of New Orleans.
If the Brits had taken control of the mouth of the Mississippi it would have changed all subsequent history.
WW2: German sub crew, New York.....Japanese balloons to start forest fires on the West Coast.....