I worked in the Senate during the debates leading to enactment of the War Powers Act in 1973. One Senator I worked for supported the measure as a way to prevent future Vietnams. Another I later worked for opposed it because it allowed presidents to engage in war without prior congressional approval for up to 90 days.
I believe the law is constitutionally legal and politically wise. I also believe that it has worked to prevent prolonged and unpopular wars, for none of the conflicts not specifically authorized by Congress has lasted more than 3-4 months,with one possible exception. The exception is the conflict in Syria, which the Obama administration says doesn't need a new law, though they have proposed one. Congress seems too divided to support the current war or to vote to limit it, but the public isn't screaming for withdrawal.
Congress in 1973 and every now and then since has become suspicious of presidents escalating small conflicts into big wars. Lawmakers voted numerical limits on military advisors in Central America in the 1980s and in Colombia in recent years. But they are willing to tolerate U.S. combat advisory roles in several countries in the Middle East and elsewhere, especially when the threat is linked to jihadists. That's one reason there won't be loud antiwar speeches or demonstrations after the revelations in the Washington Post today about the little wars special operations forces are now engaged in. Nor about the added troops and missions the NYTimes says are likely headed to Iraq and Syria.
Why no outrage? Why no suspicion that the president is getting America mired in another secret war? I guess the American people are more willing to fight the terrorist threat, and probably also more trusting of Obama because of his demonstrated reluctance to use force in a large-scale way. Whatever the reason, it's noteworthy that the dogs of peace aren't barking.