Congress might have the right to actually declare war but the President needs the power to act right now when necessary

 Imagine a first strike against us of nuclear weapons and the Congress demanding that the President cannot act against the aggressor until congress approves. By the time Congress did anything it might be 1 year or 5 years later and within 24 hours the whole U.S. and possibly Europe would already be gone.

So, trying to hamstring the President so he cannot respond whenever he needs to to American Soldiers dying from enemy aggressors is ridiculous and stupid.