The U.S. Constitution is not a suicide pact. The President is not only Chief Executive, he is the Commander-in-Chief of our armed forces. Congress has the power to declare "war", but this is a military action against a bad actor, in our own hemisphere, and does not require such a declaration. That is a matter of historical fact, with a long list of precedents.
In acting as he did, President Trump has not only removed a narco-terrorist Dictator who assumed his office illegally and seized American assets, also illegally.
There are risks involved, and our government appears to be well aware of them.
Venezuela is not Vietnam, nor is it Afghanistan. We are not fighting a war for their citizens, nor should we. We restored their chance at liberty, which all people deserve, and in the process frustrated the ambitions of the anti-American powers in China, Russia and Iran who have used Venezuela as a hemispheric proxy.
The Constitution allows the President to so act under Article 2 Section 2, and I am confident the the Supreme Court would see it the same way, as they have in the past.