Well, Putin is wrong. The US Congress can authorize acts of war regardless of what the UN wants. We don’t need anyone’s permission, much like Medvedev (with Putin’s backing obviously) didn’t need our permission when he attacked Georgia.
That said, we hope our elected representatives show proper restraint before they authorize war. They aren’t elected to simply rubber stamp whatever a president wants. Otherwise, why would they need to even vote in the first place? If they’re a rubber stamp, they’re basically handing the power to declare war to presidents. All hail King Obama, eh?
I agree with your major premise. I guess it was Harry Truman started us down this tradition of undeclared war. It’s a blight upon the Republic.
I believe that is the key point. They are elected to look after the USA and it's citizens. That is their priority.
Spending a fortune on a foreign civil war where both sides hate us, with money we have to borrow from another adversary of ours?
How could that be in "our" best interest?