What was a significant event during Obama's presidency?

The passage of the Affordable Care Act (ACA), also known as Obamacare, is a significant event during Barack Obama's presidency as it represented a major overhaul of the United States healthcare system. Enacted in March 2010, the ACA aimed to reduce the number of uninsured Americans, improve healthcare quality, and control healthcare costs. It established health insurance exchanges, expanded Medicaid eligibility, mandated that individuals obtain insurance, and prohibited denying coverage due to pre-existing conditions. This legislation was a pivotal aspect of Obama's domestic policy agenda and had lasting impacts on the healthcare landscape in the U.S., making it a central achievement of his administration. Other events and policies from different time periods or administrations, such as the siege at Waco or the implementation of NAFTA, do not relate directly to Obama's tenure.