The answer is: lived in English colonies, subject to English law. The English Bill of Rights and the Glorious revolution took place in the 17th century. The American war for independence took place between 1775 and 1783. And Americans were not ignorant to what was going on in Europe; because, although communications back then were slower and difficult, there was commerce between America and Europe.
The legislative branch represents the will of the people for passing laws and funding the government, and the executive carries out the laws and the judiciary declares conflicts between laws and sometimes declares laws invalid.
