I doubt that high speed rail will work in the midwest, or that it would be inexpensive.
Even aside from the efficiency, I bet there would be a significant cultural impact on the entire Midwest if it were suddenly possible to travel across long distances quickly and inexpensively by land.
Long-distance relationships would be easier to start and maintain.
Folks who think legalization of drugs, sex work, etc. means the breakdown of society would be able to visit places where it obviously hasn't.
Folks who think red states are nothing but right-wingers and dismiss them as "flyover states" would be able to see and converse with the left-wingers who struggle every day to make their states less red.
People would be dramatically more free to switch jobs and find a new place to live, with the ability to visit easily and repeatedly beforehand.
Generally speaking, geographic mobility enables social and cultural mobility. Everybody who thinks you should travel to broaden your horizons knows this, but currently any significant travel is effectively off-limits if you're disabled and/or on a limited budget. If broadening your horizons is so grand, shouldn't they get to do it as well?
Blue-sky speculation -- given current technology, and reasonable extrapolations of how it will improve over the next decade or so, as opposed to assuming some game-changing invention will come on the market before then -- I think the best bet would be: step one, improve American internet structure so that fast reliable internet is available everywhere, even in "the sticks," possibly via a new version of the New Deal Rural Electrification Act that brought electricity to the whole country, even "the sticks." That would make "remote work" possible from anywhere in the US -- and, more importantly, would mean anyplace in the US already has the infrastructure necessary to support viable businesses coming in.
Once the number/percentage of people who MUST live in a given area for their job has been reduced (though not eliminated, of course), alongside an increase in the number of places where businesses might reasonably spring up to support population centers, people's chosen migration habits will then indicate where transportation lines should be extended. In other words, make a series of "somewheres" first and then build rails to connect them, rather than building railways to "nowhere" in hope that the railway itself will make that "nowhere" become a "somewhere."
Though in the long term, there's also the problem of climate change; I suspect that a LOT of currently habitable places in the US will be too hot to live in a century hence; OTOH, at least a handful of currently uninhabitable/undesirable places will become nicer and more clement. End result: we'll be seeing a lot more internal migration from climate change alone, over and above and purely economic/career-motivated moves.