Corn in the US is mostly used for harmful purposes. It's used for producing fodder for intensive cattle farming (which of course produces lots of CO2). It's used for biofuel production, which as the article observes releases more CO2 than that it saves. And it's used for producing corn syrup which is an ingredient that nobody needs in their diet. The rest, which would be usage for e.g. corn bread or other staples of…
It's kinda hard to kill those subsidies when farmers have been used to them for 50 years, and it's a big political sticking point. The USDA exists to create more export crops. For the US, this might challenge that. That's also why the FDA can never rule that sugar or HFCS is harmful, it's a major American product, and that would be admitting that it's faulty.
"Just because you've always done things this way does not mean it is not incredibly stupid."
So, yes change is hard. But we need to change and this is kind of an obvious change to make. If we wait for the FDA to conclude that corn syrup is bad for you, we can indeed wait a long time.
So, don't wait for them and adjust their priorities at the federal level. That's what governments are for. You can't expect these agencies to do reasonable things by themselves when they are obviously stuck protecting the very unreasonable status quo. Bloat is the problem both in these agencies and the obese citizens whose interests they are supposed to protect.