How President Trump's Jerusalem announcement upsets the status quo.
Both Israelis and Palestinians consider Jerusalem as their rightful capital. Jerusalem is home to important holy sites for all the Abrahamic religions, and so it has become a critical bargaining chip in the ongoing discussion between Israelis and Palestinians.
President Trump's administration announced in 2017 that it would officially recognize Jerusalem as Israel's capital, and that it planned to move the U.S. embassy to Jerusalem. This would make the U.S. the only country in the world with an embassy to Israel in Jerusalem - there are currently various consulates, but no embassies. The announcement spurred condemnation from various countries, including U.S. allies, and has quickly become a political flashpoint of the Middle East.