Well the history of democracy is very short compared to monarchy. Let’s check back in on this in a few thousand years to see how both fare.

Plenty of research supports this, for example this trying to find why so many new democracies result in civil wars:

https://www.jstor.org/stable/20752195?seq=1#page_scan_tab_co...

By comparison England lasted from 886 to 1642 without open civil war. At the extreme Harappan civilization seems to have lasted 2,000 years without an open civil war or really any major wars.

Except for the Hundred Year War, the War of the Roses, and the many other smaller English civil wars.

But yes, if you exclude all the civil wars then England had no civil wars during that time period.

It’s a common terminology: https://en.m.wikipedia.org/wiki/War_of_succession#Terminolog...

Hundred Year War is hardly a civil war existing as it did between multiple countries.

Smaller conflicts like Buckingham's rebellion are excluded much the same ways as I ignored most of these: https://en.m.wikipedia.org/wiki/List_of_rebellions_in_the_Un.... Along with a host of unmentioned smaller slave revolts.

The War of the Roses was is arguable if it’s a civil war. I and many others disagree (see above Wikipedia link).