One key problem with the Spanish and Portuguese colonies is not just that they were more feudal; they were more absolutist. Vast tracts of land were held by the elite, whereas in the English (and, to a much lesser degree, French) colonies, small holders were much more common. That's certainly a good recipe for unrest, but not a good recipe for an organized revolution, nor for a stable society afterward.
I remember a passage in Wealth of Nations where Smith comments that the most liberal and free areas in the Spanish and Portuguese colonies were the capitals, because thats where government agents could most easily check each other and the rule of the King was most solid. When you're relying on the authority of an absolute monarch to protect your liberty, your society's got a few cracks.