Impeached, is that too strong? I dunno. Probably not. We impeached former President Bill Clinton for perjury. Do you think violating the Constitution and the War Powers Resolution of 1974 is stronger reason than perjury?
Article 1, section 8 is pretty clear:
The Congress shall have Power ...To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water;
(that did not say The President, it said The Congress)
And beyond that, he clearly violated The War Powers Resolution of 1974 which didn't necessarily require Congressional approval, but only that the president consult congress.
What The Fuck?