1783 Treaty of Paris In addition to OTL US, the infant republic also acquires New Ireland(New Brunswick), Bermuda and all land south of the St Lawrence River.
1812 US claims Falkland Islands
Treaty of 1818 US acquires all of Oregon territory.
Adams-Onis Spain sells Florida to US
Treaty of Guadalope Hidalgo In addition too OTL Mexican Cession, the US acquires Baja California, Chihuaha and Coahuilia(sorry if mispelled)
1853 US annexes Formosa and Hawaii
1850's US annexes Greenalnd, Danish West Indies from Denmark after dispute over passage fees on the Kattegat.
1867 US purchases Alaska from Russia, purchases Rupert's Land from Britain in addition to forgiving claims of damages inflicted by Confederate raiders.
1869 US purchases Dominican Republic
1898 US annexes Cuba, Philippines, Puerto Rico and all Spanish Pacific territories.
1920 US leases Kamchatka from Soviet Union for 60 years
http://http://query.nytimes.com/gst/abstract.html?res=9502E6DA163CE533A25753C3A9679D946195D6CF
1941 Under 1941 lend-lease agreement Soviet Union cedes Kamchatka to US.
Thoughts so far?