Final answer:
The Patient Protection and Affordable Care Act added Medicaid expansion to the U.S. healthcare system, increasing coverage for lower-income individuals.
Step-by-step explanation:
One feature that the Patient Protection and Affordable Care Act (PPACA) adds to the healthcare system in the U.S. is the Medicaid expansion. This expansion aims to cover more Americans under Medicaid, particularly those with lower incomes who were previously uninsured or underinsured. The PPACA, commonly known as Obamacare, also includes other key components such as requiring individuals to have insurance or pay a penalty, protection for those with pre-existing conditions, and the introduction of subsidies to assist with insurance premiums.