Iran would have become a nuclear power had President Obama not united most of the world in boycotting Iranian oil sales, which crippled Iran's economy and forced it to negotiate. Other presidents tried to stop Iran's nuclear program. They failed. Obama succeeded.
High-quality health care is not available to millions of Americans who don't have health insurance, or whose substandard plans provide minimum coverage. That's why the Affordable Care Act is so important. It provides quality health insurance to both the uninsured and underinsured.
Jim Crow laws stripped blacks of basic rights. Despite landmark civil rights laws, many public schools were still segregated, blacks still faced barriers to voting, and violence by white racists continued. Such open racism is mostly gone in America, but covert racism is alive and well.