“The passage of the resolution, however, does not mean foreign forces will immediately be expelled from the country. The country’s prime minister would need to sign off on a formal bill to accomplish that. Mahdi, of course, supports the move, but the fact that he is an interim prime minister could complicate matters.”
https://www.vox.com/world/2020/1/5/21050449/iraqi-parliament-expulsion-us-troops-soleimani-killing