Wars are "Declared" only against sovereign nations in order to formally notify them that a state of war exists between two sovereign states. The Declaration of War was a diplomatic courtesy which, before the CNN era, prevented accusations of "sneak attack" as happened when the Japanese Embassy in Washington could not type fast enough to deliver the Decalration of War to the White House before the Imperial Japanese Navy delivered it's bombs to Pearl Harbor.
A Congressional Authorization to Use Force fulfills all the Constitutional requirements regarding the war making powers of Congress.
Neither the Taliban militia nor the Al Qaeda terrorist network is considered a sovereign nation and therefore a declaration of war is not appropriate.
Likewise, the United States never considered the Confederate States of America to be a sovereign nation and war was never declared by Congress during the Civil War.
Homework assignment: Find the Declaration of War of the Civil War. You can use Google.
Prior to the Barbary War, Congress debated whether or not to declare war on the Barbary States. Congress decided that the Barbary States were no more than a collection of pirates and to declare war would dignify them with the status of sovereign states. Therefore, Congress refused to declare war and instead passed an Authorization to Use Force.
In the same Barbary War, President Thomas Jefferson stated that a declaration of war was unnecessary, whether the Barbary States were sovereign states or not, because the Barbary States had already caused a state of war to exist by attacking the United States and therefore a state of war already existed. In other words, Thomas Jefferson recognized that a Declaration of War was a diplomatic courtesy between sovereign states before the bullets started flying.
Be that as it may, Obama did not even bother to get an Authorization of War in the case of Libya.
I think it would have been appropriate to declare war against Afghanistan following 9/11, and I would have liked to see Bush request such a declaration from Congress.
I agree with most of your post. Furthermore, I would go so far as to say that the author of original article is in error when stating that a U.S. Declaration of War must be based on an overt act of war by another nation. While it might be unwise to do otherwise in most cases, I see no legal or Constitutional requirement for it.
However, it is incorrect to state that there was no Declaration of War against the Barbary pirates. A Declaration of War against the Bey of Tripoli was passed on February 6, 1802.