Only the federal government can sign treaties.
Hope that helps.
Quite simple they were outnumbered by the Mexicans 1800 to 185 and they were outgunned.
The answer is c. Civil War. The states of the South were
against any interference from the Federal government particularly on the issue
of slavery. When Lincoln was elected,
the Southern states felt that their rights to own slaves would be jeopardized and
this would lead to Civil War.