US Presidentialism Only Works in the US

Per Adam Przeworski's comparative research, the American-style system of presidentialism and separation of powers has only really worked in the United States; the many countries that copied it (all of Latin America) failed, because parliamentary systems have an escape valve—a vote of no confidence triggering an election—that presidential systems lack, allowing a hobbled party to stagger on while resentment builds, and the historic ideological overlap between US parties was part of what made the exceptional American system work.