This one is Easy. The USA wins the war of 1812 decisively and the War Hawks Become more popular. Jackson's Democrats are much more Jingoistic.
So War of 1812: We get the Maritime Provence of Canada. We don't have the Navy to demand anymore.
Mexican War: They just annex more mexican states and create "protectorates" in Central America.
54'40 or fight!: We fight, Canada tries really hard, but damned those Yankees are blood thirsty.
Onsted Manifesto: We fight, (We have a navy now because President Clay in 1832), Spain loses. Gives up islands. England Loses Caribbean, usa Annexes Dominican Republic.
US Civil War: The CSA includes Cuba, Dominican Republic, and the four north eastern "mexican" states Cohuala, Nuevo Leon, Tamulipas and that other one that isnt on the map i looked up. War goes about the same because the South is still agrarian.
1868: Sweards Icebox, Russia figures Better Yankees than Brits.
1917: The USA and the Uk join forces to fight Germany (because butterflies didn't cross the Atlantic due to a polar vortex)
1941: Denmark is Invaded, Canada and the US Split Greenland.
1945: Denmark is Liberated, Canada and USA Keep Greenland.