The Sons' agenda is the dissolution of the Empire in its entirety. Canada, Mexico, and Central America given their status as sovereign states back. The Sons of Liberty, being the direct continuation (one of them) of the United States military, most likely expect to have a hand in the creation of the new American state. They would most likely oppose the partitioning of the country along factional lines. After all, pre-Imperial America had its fair share of factionalism. They'd rather cooperate with the Southpaws (and more begrudgingly the distant Ceresians and Antarcticans) than act against them.

Also, I'm cooking up another post.