Political conservatives were worried about people being upset due to the large number of US soldiers(117,000) who died fighting in WWI.
A characteristic that all state constitutions have in common is that they all "include a bill of rights". These bills of rights were included to ensure that the government did not trample on the natural human rights of the citizens.
The Magna Carta is considered to be the foundation of English freedom mainly due to the fact that it allowed barons and other high members of court to oust a king or queen if he/she was abusing their power.