Just to elaborate a little on this: I don't think that UCI prize money should be blamed here, but it's crazy that there's zero, if true. (prize money is mostly incidental for riders at the WT level at any rate).
But but but -- to speak to the issue at hand -- the US is the birthplace of gravel, as it was for MTB, and surely the US national team can figure out that if you support your riders on the international level it would be a positive thing for US cycling in general. I know the initial reaction to the UCI hosting a GWC was a bunch of snickering, but like it or not, the UCI is the only global sanctioning body, and the race has the potential to be more and more prestigious. Of course, it might just muddle along but there's also a distinct possibility that riders like MvdP and WvA or even Pog (who has dabbled in cross) will be mixing it up in a new discipline eventually.