Since the U.S. is operating at a deficit, that means the U.S. borrows the money, transfers it to an Israeli Federal Reserve Bank account, and pays interest on it long afterward, while Israel makes interest on it. See the Congressional Research Service report for details.
In addition, Israel frequently receives more money and perks: loan forgiveness programs, weapons subsidies, special trading privileges, etc. When the Pentagon refuses to turn over to Israel weaponry that the U.S. needs or technology that is classified, Israeli leaders go over the generals' heads to pro-Israel Congressional representatives, who procure the desired items for them.
The cost of supporting Israel has been astronomical. An economist contracted by the Army War College found that the total costs, both direct and indirect, amounted to $3 trillion. On top of that is the cost of the Iraq War – at least $3 billion – which was largely promoted by Israel partisans.
Through such American subsidies over the past 60+ years, Israel’s current account balance is 29th in the world, while the U.S. has dropped to 196th. Yet, American tax money continues to flow to Israel.
The Cost of Israel to the American People, By Richard H. Curtiss
Israel is an extreme liabililty for the U.S. financially, strategically, politically, By Ambassador Chas Freeman
US taxpayers paid more to Israeli defense budget than Israelis, By Alison Weir
American taxpayers subsidize Israel's ascendancy over the US, By Alison Weir