Although the Affordable Care Act hangs in limbo, many uninsured Americans live in states that do not have an exchange for the federal health care law.

According to a new Census Bureau report, 15.4 percent of the total population lacked health insurance. Of those 48 million Americans, nearly 60 percent lived in states that have chosen not to set up their own insurance exchange under the federal health mandate, commonly known as Obamacare.

The insurance exchanges allow people to compare different insurance plans and buy coverage. Currently, the enrollment period opens Oct. 1. Under the new federal health care law, most Americans are required to have insurance by January 1, 2014, or pay a penalty.

Originally, states were expected to set up and run their own online insurance exchanges, and not rely on a federally run exchange. However, according to the Kaiser Family Foundation, only 16 states and the District of Columbia have made their own exchanges. Seven more states are partnering with the federal government to operate their exchanges. In the other 27 states, people without insurance will use federally managed exchanges to shop for coverage.

The majority of the nation's uninsured live in the 27 states that do not have any health insurance exchanges set in place. Many of those states have actively opposed the new health care law.