re: All the time; it's a matter of chronology
It's a process.
Mary Anne has it right.
The English had the Magna Carta (1215).
French thinkers like Montesquieu (1750) proposed the division of powers (legislative, executive and judiciary.
That influenced the American constitution which in turn influenced the French constitution which influenced the Belgian constitution, etc...
It's a process and the US was one of the steps, not the first nor the last, just part of the process.
Raoul