Article: By the late 20th century, the majority of the world's countries had a prime minister or equivalent minister, holding office under either a constitutional monarchy or a ceremonial president. The main exceptions to this system have been the United States and the presidential republics in Latin America modelled on the U.S. system, in which the president directly exercises executive authority.

Question: In the U.S. and governments modeled on it, who holds executive power?
president