International Affairs covers everything the US federal government spends outside its borders: diplomatic operations (the State Department's roughly 270 embassies and consulates), foreign aid (USAID development assistance, PEPFAR global health, humanitarian relief), and military assistance to partner nations (Foreign Military Financing — Israel, Ukraine, and Jordan are typically the largest recipients).
The total is around $73 billion in FY2024, or roughly 1% of federal spending — a fraction of the share most people guess in polls. About $35B flows through USAID for bilateral aid programs, $20B funds State Department operations, $8B goes to FMF, and the rest covers UN dues, refugee admissions, and international broadcasting (Voice of America, Radio Free Europe).