'to all extent and purposes' means that it is correct for every possible scenario, so from what ever angle you were to look at it it would be true.
To the extent you let it. Everything depends on the situation.
pretty much all of Europe, north and south America, Africa, and some countries in Asia were at war.
The kings decided life and death issues, went to war, waged taxes, and took the best of everything. That makes them pretty powerful.
North America