I’m sure you are aware of this, but it still needs to get posted in this thread.

The politics of it is that appropriations in support of troops in the field are on a track called “must pass.” Indeed, one of the favored legislative tricks to get something you want is to contrive a rider on a must pass bill that nobody notices. It’s an ancient move but it still works on occasion.

The politics of “must pass” is that if you vote against such a bill you are stabbing the troops in the back — a treasonous move.

Bush II took it to a whole new level by pulling war funding off the budget (to make room for a tax cut) and funding Iraq with continuing resolutions. Obama had to take a PR hit when he put Iraq back on the budget — it made him look like a spendthrift when he was only undoing the trick you might call putting the war on a separate credit card.

“Plain language” is not a useful method of constitutional interpretation because (among other reasons) there are just too many cattle already out of the barn.

Take, for example, the 7th Amendment.

And after you look at that, ‘splain me the doctrine of “selective incorporation.”

While I’ve not done the research and so I’m talking out my ass a little, I’m not convinced that the purpose of the provision you cite is to backstop congressional responsibility for declaration of war. It would be a more parsimonious explanation that back when it was written the military did not need to come back to the well so many times to fund something on the level of, say, Mr. Jefferson’s action against the Barbary Pirates. Just speculation, and even if so, it does not excuse Congress abdicating its authority because voting on an AUMF (for or against) is perceived as being too politically risky.