In the 18th Century, nation states declared war on each other and went at it. That is the context to the USC's provision about declarations of war. In modern times nations like Venezuela and Iran conduct war, undeclared, using proxies. Some proxies are like Hamas and Hezbollah, which Iran funded and armed. Some proxies are like the drug smuggling orgs that smuggled deadly drugs and criminal thugs into the US, with the support and participation like Venezuela and Maduro.
Situations where proxies wage undeclared war are covered by the War Powers Act, and from what little I've heard, Trump's move complies with that.