The Civil War of 1812
From the Pritzker Military Library website:
"The Civil War of 1812 sheds light on the tangled origins of the relationship between the United States and Canada. In a world of double identities, slippery allegiances, and porous boundaries, the leaders of the young American republic and the British empire struggled to control their own diverse peoples. Soldiers, immigrants, settlers, and Indians fought in a northern borderland to determine the fate of a continent. Americans were divided anew, between former Loyalists and Patriots, fighting alongside native peoples defending their homelands. Serving in both armies, Irish immigrants battled one another, reaping charges of rebellion and treason, while dissident Americans flirted with secession and aided the British as smugglers and spies.
After fighting to a standstill, the Americans and the British were forced to coexist. Taylor concludes that, by ending in a stalemate, the War of 1812 provided assurance that both sides needed—that they could survive each other’s presence on a shared continent, and could settle later border disputes without recourse to another war."