The US would spin it as "we didn't know Abdul-Mahdi was meeting with Soleimani whom we were ACTUALLY targeting so we unintentionally killed BOTH of them, turns out Abdul-Mahdi was an Iranian stooge the whole time and was probably in on the terrorist attacks Soleimani was planning" or something to that effect. Plus, something about freedom/democracy for Iraq.

If the US dollar lost reserve currency status, things would get bad for the US.