system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why is it common for developed western countries to hold snap elections but the US doesn't.
gpt
The US uses a presidential system while most other countries use a parliamentary system.  These systems differ on who elects the executive branch of the government.

In a presidential system the executive branch of the government (ie the president) is directly elected by the country's citizens.  Once elected, the president serves out their term regardless of their popularity.

In a parliamentary system there is no election for the executive branch of the government (ie the prime minister).  Rather, the prime minister is chosen by parliament and serves only so long as they retain 51% support in parliament.  When the prime minister no longer has sufficient support in parliament then one of two things can happen: either parliament selects a new prime minister (which is rare) or the government just doesn't have an executive branch until the next election.  

Because the government can't function without an executive branch, the solution that parliamentary systems have come up with is the ability to hold snap elections to replace the entire current government and start over again from scratch in the hopes that the new government will be able to select a new executive branch.