This is only my second post and my first TL so please be gentle!
1. Alexander Hamilton is killed leading his forces in action at Yorktown. The war is successfully concluded and the Articles of Confederation establish the government.
2. Without Hamilton, the Constitutional Convention of 1787 fails to amend the Articles. The Union does not dramatically dissolve, but regional sovereignties begin emerge in the form of New England, Southern Confederacy (VA/NC/SC/GA), and United American Republic (PA/NY/NJ/MD/DE).
3. This allows the regional neighbors in Canada and the area west of the Appalachians to play the states off each other. These threats Over time these threats force the govts to develop into distinct nation-states. This creates a North America with several distinct states and empires.
I look forward to comments and criticism. Also, let me know if this same POD or idea is floating in the ether somewhere else.