In it's early years, The US President Jefferson attempted to buy land from Emperor Napoleon I. However the negotiations failed and The US never spread out beyond The Mississippi River. Betwen the river and the Pacific are Republica California, The Republic of Texas, The Republic of Deseret, The Dominion of Columbia, Kingdom Of Louisiana and The Confederation of Tribal Americans.
So here is my WI. WI The Purchase of French Territory had succeeded and the USA annexed the entire Louisiana Territory. Could the US have spread out farther West?