The difficulty is convincing even a plain majority that we should take any action. We lack that in the US.

In the US, you've also got the problems of: not all votes count equally (Senate, electoral college) so some people's opinions (say, those in Wyoming) count a whole lot more than others; you need 60 Senate votes to do anything remotely controversial, and that's the same body subject to the first problem, so even 60% support for a position among the general population may not be enough to make something happen; our voting system forces people to compromise lots of things they care about, in favor of a few things they care about a whole lot, so you're never going to see someone who's, say, very pro-life but nonetheless cares about climate change, vote for action on climate change at the expense of their pro-life position.

I think the majority believe that action should be undertaken. The trick is figuring out what action.