If suburban drivers and homeowners weren't benefitting from urban success and externalizing all their costs then those properties would already be close to worthless.
It is my understanding that many car dependent suburbs got subsidies from higher levels of government to build new roads [0], which allowed them to expand their tax base, but that the density of their taxpayers, per mile of infrastructure, is not enough for longer term expensive maintenance after several decades. This applies not just to roads, but also water and sewer infrastructure. Cities with ten times the density of suburbs have an easier time paying the fixed per-mile portion of infrastructure costs.
The infrastructure in suburbs has already been subsidized, and may need more subsidies. Or services will degrade.
I don't know that anything you said above conflicts with what you said about mixed use, I wasn't sure about the funding part though.
It's also a vicious cycle: making public transit marginally worse increases the number of people who drive to get places, which makes the government build more roads, which makes cities sprawl more, and eventually you end up with a city like Atlanta that spans 50 miles and is barely navigable without a car.
Yes, it will piss people off - it will make cities MUCH less convenient for suburban drivers. That's not a bad thing unless you happen to be a suburban driver.