1812: Canadian colonies rebel against British rule and join the United States. Upper and Lower Canada join as Quebec and Ontario, and British North America is gradually integrated.
1846: Bahamas is purchased from Britain while the Oregon Country/Columbia District was completely ceded.
1848: Northern Mexican states request annexation after the American victory, so the US obliged. Baja California was purchased by James Gadsden and admitted to the Union as the State of Sierra.
1867: Greenland is purchased from Denmark along with Alaska from Russia as a part of William H. Seward's expansionist plans.
1946: The Philippines takes a vote on the matter of independence. Eastern Visayas is the only region with enough votes to remain part of the United States, so it becomes a territory while the rest of the country is given it's independence.
Liberia is kept as a territory, and the geopolitical climate is not nearly as dire as it is in OTL.
The Canal Zone is never returned to Panama because Pierre Trudeau was president instead of Carter.
French Guiana is purchased at some point.