what political models from America were used to create the constitution?

Answer 1

At the time the constitution there were no other "democratic" nations.
They were all written under the premise, as written in the Declaration of Independence, that all human rights are given by God not by the government. Therefore, the Constitution limits the rights of government on the people rather than the other way around.

Answer 2

Ancient Greece, Republic of Rome, and the Iroqouis Confederation helped influence our demoractic principles. For the constitution, the Magna Carta and the works of John Locke, Montesqui and other enlightenment figures..