If the Roundheads win, New England is unlikely, but would Virginia (+Maryland) have the capability to try to go at it alone as a sort of "England-in-exile" if the English Commonwealth never allies with France against Spain?Would an independent New England or something to that effect be possible during the English Civil War?
Any of the Conquistador leaders could have realistically detached ties with Spain and become fully independent.I believe there were several plots by the sons of Cortes attempting to seize control of New Spain and found a new kingdom.