What would single payer health care look like in the US?

You might think it's not possible but I'm here to tell you that it is.  It's just not possible as the thing you are thinking about. Instead it's this. 

The fragmentation of American health care has kept Big Data from being fully harnessed as it is in other industries, like online commerce. But Optum’s acquisition of Change heralds the end of that status quo and the emergence of a new “Big Tech” of health care. With the Change data, Optum/UnitedHealth will own the data, providers, and the network through which people receive care. It’s not a stretch to see an analogy to Amazon, and how that corporation uses data from its platform to undercut third parties while keeping all its consumers in a panopticon of data.

The next step is up to the Department of Justice, which has jurisdiction over the acquisition (through an informal agreement, the DOJ monitors health insurance and other industries, while the FTC handles hospital mergers, pharmaceuticals, and more). The longer the review takes, the more likely it is that the public starts to realize that, as Dartmouth health policy professor Dr. Elliott Fisher said, “the harms are likely to outweigh the benefits.”

It's not politically possible to get the benevolent One Giant Public Health Behemoth controlling costs and care on behalf of patients.  So we will have to settle for the One Giant Private Health Behemoth controlling everything on behalf of executive profits. But at least it will be a "market-driven" solution that gets us there so it must be good.