New York City pledged this week to pay down $2 billion worth of residents’ medical debt. In doing so, it has come around to an innovation, started in the Midwest, that’s ridding millions of Americans of health care debt. The idea of local government erasing debt emerged a couple of years ago in Cook County, Illinois, home to Chicago. Toni Preckwinkle, president of the county board of commissioners, says two staffers came to her with a bold proposal: The county could spend a portion of its federal pandemic rescue funds to ease a serious burden on its residents. In 2022, Cook County became the f…