If Spain had its own version of the English Civil War or whatever revolution that led to a Spanish version of a Magna Carter, a constitutional and secular government, and all the aspects of the English government of the 17th-18th Centuries that was relatively progressive for its time, how would this affect Spain and its colonial empire? And can this be possible?
If that is the case can we see Spanish Latin America being better off without the OTL caste system?
What kind of time frame are we looking at?
The Magna Carta was 400 years before the English Civil War.
Anyway, in my opinion, it would have to be well before colonization starts, since the king sharing power with the nobility is almost always a product of the king being broke, and once all of that American gold starts flowing into the King of Spain's coffers, no one else will be able to approach his power.
In my opinion, you'd need to completely change the Reconquista - which shouldn't theoretically be impossible. Have the King of Spain be a relatively weak figure, with no wealth, only military authority during the Reconquista...or have a more "international", Crusade-type feel to it...
Unfortunately, I'm not familiar enough with the history of that place and period to expand further.