I don’t think that’s true. What US voters don’t want is the level of care you get from a doctor who takes Medicaid. A single payer system can work here but because of how bad the “poor people doctors” treat patients it’s going to require some convincing.
A small minority don't want it, so they've spent a lot of money and effort to misrepresent what it's effects will be (see Wendell Potter's admission of this) to scare gullible voters out of wanting it. Even then, if it were in a national referendum it could pass.