Zivotofsky v. Kerry: The Supreme Court case over Israel and US foreign policy, explained - Vox: The primary reason that the court will likely side against Zivotofsky is that the Constitution is widely understood as giving the executive branch the bulk of foreign policy powers. That derives from something called the "sole organ" doctrine, named for a speech that founding father John Marshall gave in 1800, a year before he became the chief justice of the Supreme Court. Marshall said, "The President is the sole organ of the nation in its external relations, and its sole representative with foreign nations." A 1936 Supreme Court decision, United States v. Curtiss-Wright, ruled that the "sole organ" doctrine grants the president inherent constitutional powers in foreign relations.
Those inherent presidential powers are considered to include authority to recognize countries and borders, which is central to the Jerusalem issue. The idea is that the US government needs to be a single unified entity on the world stage in order to conduct effective foreign policy. Letting the president and Congress independently set their own foreign policies would lead to chaos.