FillyofDelphi
Banned
Firstly, I doubt the Puritans would perform a reign of terror, as the Puritans were primarily Gentry, and Merchants, the majority of the Rural Population remained Pseudo-Catholic, and even Pseudo-Pagan, for a long time after the civil war. Secondly, the Levellers never had the population to perform a reign of terror, the thing that spooked the Gentry/Merchants about them was that they existed, and doubly so for the Diggers, in fact a key part of Cromwell's Consolidation of power was his crushing of the Army Agitators. Similarly, a Stuart Victory arguably would prevent the rise of so-called Classical Liberalism, and would lead to English Liberalism, and thus American Liberalism, being about comparable to France, from the start. A further complication is that with a Stuart Victory the Northern US Colonies would likely become more Puritan, from refugees, this would likely form a divide between the North and South, that coupled with the Settlements in Canada, would prevent any type of American Independence. The Other issue is that at this time the key reason for the Strife, was the Parliamentary Control of Taxes, which if he had won Charles would have likely gotten greater control of, this along with Loans would then allow for Continental Wars, and colonial wars, likely more with the Dutch, and it is hard to predict, if these would have the same outcome as under Cromwell, and Charles II.
Touche. I readily concede that the current of the Civil War needs to take a fundimentally different turn in order to result in the kind of political-cultural point we'd need, and the Levelers aren't the right tool to do that (being too ideologically radical for mass appeal). Perhaps the Civil War's middle stages become a more dragged out affair over the countryside, allowing political disagreements to fester in the Parlamentarians between the more Puritan/Radical members who want to impose major reforms on British society as a whole and those of a more moderate bent who're willing to tolerate the old ways of broader society and keeping the basic systems intact? This could result in the later trying form a parallel force to the New Model Army under their own control, which could be based on co-opting and training/equiping formations of Clubmen (who'd have,due to the more drawn out war, more plentiful and organized into clearer and easy to negotiate groups under the more popularly supported local Gentry and clergy who's doctrine best meshed with popular local practices, as opposed to a centeralized state church). If this breaks out into the schisming between the two sides, you could get a reign of terror from the Puritans NMA against precisely these kinds of psuedo-Catholic regions to try to intimidate the masses against joining/supporting the Clubmen: killing multiple birds with one stone by opening the door for the Royalists to regain the upper hand, baking the culture of popular participation/will into the national history and certain factions of the intelligencia/powers, and creating a recognition and fear of the power of the masses and merchants that would cause the aristocracy to keep the franchise and access to power limited and form their own expensive standing army as a tool of royal absolutism after seeing how it could be used to keep the masses in line. Do that, and you have a chance of producing a system that at some point makes conditions not too dissimilar to those in pre-revolutions Italy that, like them, could find success with a French sugar daddy.