Question

why there is no PM in U.S.A.

Answer 1

Because, by the decision of the framers of the U.S. Constitution, the United States doesn’t have a Westminster Parliament like Britain and Canada, it’s a presidential republic. Most of the same pieces are on the board in both systems, but the rules are different. So the Kings, Queens, Bishops and Pawns can’t move the same way and don’t have the same jobs.

In Canada the head of state is the Queen of Canada, as represented in Ottawa by the Governor-General, who is also the Commander-in-Chief of the Armed Forces. As a Constitutional Monarchy, though, Canada is not governed by the monarch or the GG, it’s governed by the political party which won the most seats in Parliament in the most recent election. Currently that’s the Liberal Party of Canada. The leader of that party, Justin Trudeau, is automatically also the Prime Minister and the head of government. In practice (though not in theory), the Canadian systems combines the legislative and the executive power into a single body, Cabinet, as led by the Prime Minister, both of which are answerable to Parliament.

In the United States, the elected President is the Head of State, the Head of Government and the Commander-in-Chief of the Armed Forces. He or she holds executive power.

Congress holds legislative power, so the two are broken up and are more adversarial than they are in the Parliamentary system. However, theHouse Majority leader (the recently resigned Paul Ryan, presently) would be Prime Minister if the United States had a Westminster Parliament, in that he or she is the leader of the majority party in the House of Representatives.