The position which is considered a sort of "back up" role to the president is actually the head of the senate?

The Vice President serves as a "back-up" to the President, who also serves as the Head of State (President of the Senate, presides over joint Congress sessions).

In the presidential line of succession, the Vice President is the second in command.

"a government in which power is divided between state and national levels". federalism is a system of government in which entities such and state and province, share power with the national government.