Doesn't matter. what Pakistan would have thought, since W never ordered it. Same goes for all of that stuff about brown people, and "ragheads," and the rest. And I think lots of people are pretty smart about "blowback," whether or not they use the word. Nowadays, people are very conscious about it. At other times, they may have other priorities, or it may even seem to them that being the blowbackee beats being the blowbacker 999 times out of 1000.
According to the Wikipedia history, the Kurds were effectively on Iran's side during the Iranian invasion that Iraq fought off with massive use of CW.
The timing of the Halabja attack was, in its way, very shrewd, and it is, of course, rarely recalled in full context - not to excuse it, but to understand how it happened. Considering the use we eventually made of it, in the Gulf War, throughout the '90s, and then again approaching OIF, and considering also the extent to which we supported, protected, and enabled the Kurds subsequently, it's not clear that Halabja really went unavenged - which is why it's also too early to draw conclusions about East Ghouta. But blaming Kerry, Biden, Pelosi for being softies for voting against the Gulf War Resolution 2+ years later, when it was not about Halabja or the Kurds but about Kuwait, seems a little unfair when you recall that Ronnie was still Prez when Halabja happened and went right on supporting Saddam until the war finally ended.
You ever run into a good history of the Iran-Iraq war?
I'm not sure that WMD in a U.S. city is "the" question. Probly a major WMD use in any Western city, maybe some types of attack in any city at all, would be epochal. I do suspect our response to 9/11 has had a deterrent effect on actors who might otherwise be more likely to help facilitate attacks, whether or not it made an impression on hardcore AQ.
Not sure about Baghdadi.
"Global hegemony" is a term I'll be trying to avoid, since I don't think it really fits the neo-imperial model, though the logic of hegemony does come into play. As for your question, as a purely pragmatic issue we can achieve via conventional weapons most of the effects we currently consider potentially militarily necessary. However, the often-heard argument in recent weeks, made by many people with whom I sympathize, that the difference between one type of weapon and another is artificial, works both ways. In the last post we observed a popular defense intellectual advocating terrorism and other unconventional modes of warfare in response to perceived resource constraints. In a world where using WMDs gets a pass, or yields benefits, or becomes relatively commonplace, it's easy to imagine the remnant taboo falling away, just as our taboo or norm against anti-civilian warfare gradually eroded during WW2, in the aftermath of multiple violations by our enemies.
As I've been saying, it such a spiral of mutual mass annihilation that our evidently fracturing global security system was or is supposed to prevent. I'm not making forecasts, I'm just observing risks and patterns. Last I heard, the Russian Federation maintains "tactical" nuclear forces to protect its otherwise too difficult to defend borders. Up until the '90s, the U.S. maintained a large CW stockpile - still not completely eliminated, it has been reported - because our potential adversaries did, just as we still maintain a large nuclear deterrent.
If, subsequent to 9/11 and the conversion of airliners into WMDs by Al Qaeda, if W had gone to the nation on 9/14 or so, and had said that the only way to prevent many more 9/11s was to use nuclear weapons in the Afghan mountains - very surgically, of course - what do you think the next day's polls would have said?