Why does the USA not have a Prime minister?

The UK has the Queen as its head of state and the Prime Minister as the elected head of government, as it is a constitional monarchy. But many country's for example France has a President and a Prime minister, Germany has a President and a Chancellor (which is the same as a prime minister), Russia has a President and a Prime minster, China has a President and a Premier (which is similar to prime minister). There is many more country's i could list. Why does the USA not a Prime Minister as well as a President like most country's, who/what takes the role of the Prime minister