First, consider the source. The mere fact that this polling is conducted by a think tank should give anyone - regardless of political party or ideological position - some pause, as think tanks are explicitly "state-external agents of change". Advocacy organizations, in other words. This is fine, such as it is, but as think tanks of all stripes present themselves as anything but ideological or partisan (including this one, the Chicago Council on Foreign Affairs) and often seek to couch themselves in the ostensibly more dispassionate language of science and academia, there's frequently a bit of a trick being played. I think we should watch out for that. It's cheesy to say, maybe, that "these people have an agenda", but these people have an agenda. They're not a university (which, yes, is also occupied by human beings who are biased), but they'd be happy if you thought they were.
Second, and relatedly, we need to look at what a think tank's interest is. Twelve seconds of Googling shows that the Chicago Council's current President was for 4 years the Permanent US Representative to NATO -- not exactly someone with a disinterested relationship to American empire and how this country treats the rest of the world, Taiwan/China or otherwise. (And NATO is nothing if not expansionist, continuing to grow -- hell, to exist -- long after its raison d'etre, the USSR, ceased to be.) I'm editorializing / speculating here, but these are the same ghouls who start every American war, the same guys at the UN handing slides to Colin Powell about non-existent (which they knew) Iraqi WMD.
Lastly there's the poll itself. I don't have time to dig into the details, but in my view the poll's results -- or anyway, the headline of its results -- fits perfectly in the steady drumbeat, growing ever louder, of civilizational confrontation with China, and the manufacturing of American consent for such a project. In my view there's some pretty straightforward Chomskian stuff happening in the zeitgeist around this, and this poll headline only serves to further it: "See? Americans are okay with confronting China aggressively!" Which of course gives elites permission to push more for these stances, a nice feedback loop. With headlines like these, they're laying the groundwork for bloodshed in the not-too-distant future. They know this full well, and they're okay with it, because neither they nor their children will be sent to die for this paranoia.
My wish for HN readers looking at this would be to be critical, even suspicious, of things like these, regardless of what one thinks about Taiwan. There's a method here.
EDIT: And, in case anyone's feeling rah-rah themselves about "defending" Taiwan, know that we'd get our shit absolutely rocked in a war with China over Taiwan. It'd be bloody, it'd be long, and we'd lose. Not to be critical of think tanks only to turn around and cite one, but plenty of entities, including RAND and the US military itself, have done war games and simulations about this scenario and it does not end well for the US. Easily googleable.