The Patient Protection and Affordable Care Act (PPACA) of 2010, popularly known as "ObamaCare" was a major reform to health care in the United States. Before passage of the ACA, the United States was known for having the highest per capita health care spending of the OECD (advanced, developed economies of the world) with distinctly mediocre results. Since the inception of the ACA, the percentage of people without health insurance in the United States has declined from 18 percent to under 12 percent and per capita health care costs have declined slightly, something that is generally good for the economy.
The ACA is also good for the economy because it makes people healthier. If people have insurance, they can afford regular checkups and preventive medicine, making them more productive economically. Children with good health care do better in school and thrive in adulthood when compared with children whose mothers have inadequate prenatal care and to children without access to regular medical care.
Almost half of bankruptcies in the United States are caused by medical bills. Unlike Canada, Sweden, Australia, or other developed countries where illness is not as financial disruptive, Americans with serious diseases may end up losing their homes or cars and struggling with the sort of debt that makes it much harder to return to a normal productive life after an illness.
Finally, you can look at the period since 2010. Although the ACA is one small piece of the US economy, the period since its passage has been one of gradual economic recovery. Although one could not claim that the ACA was the cause of that recovery (the recovery was due, among other things, to Obama's economic policies and global economic factors), the fact that the economy did recover since the ACA was passed suggest that its effects have been somewhat helpful and certainly not harmful.