Oh it would absolutely see the most obscene amount of pushback you can imagine from every corner.

Anti-big gov guys would lose their shit. Conspiracy theorists would go hog wild. Industry would be pissed that they weren't getting those sweet do nothing government contracts to "eventually" repair the roads sometime in the next ten years with multi billion dollar budgets that they could balloon ever outward and still never really deliver on.

But here's the thing. In the short term, say the first 90 days (due to statutory limitations), three words trump all others, "Commander In Chief." The president is the unquestioned top of the military hierarchy, no way around it. There are time limits, as I mentioned, that stop him from just doing whatever with no oversight from congress but if you're actually just unambiguously doing the right thing and helping people, that's really hard to argue against. And if you actually brought the full manpower and logistics might of the army to bear on a task for the full length of time the law allows you to tell congress to go fuck themselves? You could get an awful lot done, by which time the people in that affected area will have seen tangible results and now congress has to explain why they are REMOVING all of the help you were providing instead of why you were providing it in the first place.

And post civil war Reconstruction was a different animal entirely. That wasn't just about physically rebuilding infrastructure, there was a lot of racism baked in from every angle. Honestly the last 150 years of american politics would have been a lot better off if they just executed every officer and hung every plantation owner in the south rather than granting such a broad clemency for their actions, but somehow the people who actually start wars and fund them somehow aren't the ones who end up dying in them. It's a trait we got from europe, you can kill enlisted all day long and no one cares but deliberately targeting officers is somehow a war crime instead of "good strategy".