I'm not impressed with all the quotes of Iranians used to prove that the Iranians have beaten us in Iraq.
Really, who care? The Iranians believe a lot of strange things. This from a culture that considers any confrontation with the West where they are beaten into a bloody pulp but are told they'll live through their wounds as a glorious victory over the West.
Iran wants to beat us in Iraq. So of course they have incentive to talk us down. But we actually do have Iraq as an ally. Iran merely has some influence through the minor Sadrist party and their own operatives. Our departure gives Iran some more cards, but we're still in the lead. Iran wins only if we just throw up our hands and give up.
Work the problem.