It's a pretty hollow threat. Including Israel funding was the bait in the bill to get house Republicans to go along with more Ukraine funding too, which they have all decided they want to cut off and hand over to Russia. If they cut out Ukraine funding, and try to randomly drag the IRS in it too, this is just dead in the water. I do worry how they're gonna get house Republicans to agree to more Ukraine funding though.
The Republicans have no idea how to negotiate and most of the Democrats aren't easily manipulated idiots so it's likely going to take a very long time. Assuming it's even possible to get a reasonable offer out of the Republicans, which it isn't.