That's the whole point! The law requires that you "declare war".
Firing missiles at sovereign nation is an act of war. You must get Congressional approval first, as the the Constitution requires. Or you must show that the target nation is an imminent threat to the US, as the War Powers Act requires.
Congress has formally declared war exactly five times.
Yet USA has used military force many hundreds of times, though on some of those occasions Congress approved the actions by means less than a Declaration.
The first such event was the Quasi-War with France under John Adams.