Nothing
The British Cession happened because both New England and the US wanted to acquire more land.
The British cession of 1842 was a result of the Aroostook war which ended in the Webster-Ashburton Treaty.
it was not considered treason because of the way the cession happened
The French was the previous owner of British Cession. The United States purchased the western half of the Mississippi basin from France.
it aquuired on 1783
The Mexican Cession was acquired in 1848 at the Treaty of Guadalupe Hidalgo.
The convention or treaty of 1818
No current states.
they all left
British lost
The Mexican-American War, and the resulting Mexican Cession, were during the presidency of James K. Polk.
James Knox Polk