Though the criticisms of President Trump’s withdrawal from Syria have been exaggerated (see here and here), the bipartisan condemnation reflects the fact that Trump does his greatest damage to the national interest on matters that are not grounds for impeachment. When he abandons our allies, emboldens our enemies, or engages in damaging trade wars, he may be guilty of bad policy choices, but those choices are not high crimes and misdemeanors. They are matters to be judged by the voters on Election Day.
Unfortunately, our Constitution has, with the aid of Congress and the Supreme Court, created a chief executive who possesses the power to act unilaterally on the full range of domestic and foreign policy matters. With a simple phone call or tweet, Presidents can create serious problems while acting within their legal authority.
So while Congress should address Trump’s violations of the law, it needs to do much more than that. Congress needs to ensure that it prevents future Presidents from making major policy decisions on their own rather than in conjunction with other elected officials. For more on that point, see here.