The American revolutionaries took on the challenge of such a fundamental change when they proposed rebelling against the monarchy and replacing it with a Republic

Surely the American Revolutionaries were rebelling against foreign rule - I doubt if they would have felt any different if it had been a Republic in London, so long as that republic wished to exercise control over what happened in the American Colonies.

The question of what kind of constitutional system should be set up in place of foreign rule was a secondary matter - and the option of having a King was seriously considered.

Revolutions tend take on a momentum and direction of their own, and they rarely end up in the place the original revolutionaries thought they were headed. English, American, French, Russian, Chinese, Cuban... That's true of all those.