What specific trait gives the united states a presidential system of government?

A democratic government could be presidential or parliamentary. It is still a government for the people,of the people and by the people. The only difference between the two is the assignment of power of the President. In United States,the President of the country is also the leader of the executive branch. He does not have power over the legislative branch.This is done in order to distribute the power of elected politicians. This prevents any incidents of abuse of power through check and balances.