What was the key reason for the ending of the native American civilization

The key reason for ending of the native civilization of America was the colonization of North, Central and South America by the Europeans. on more reason was that the Europeans brought too many diseases with them from which the Native population had no immunity. :)

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.