The number of Americans projected to gain insurance from the U.S. health-care law is eroding, by at least 5 million people, as the Obama administration struggles to implement the $1.3 trillion overhaul amid Republican opposition. About 27 million people are expected to gain coverage by 2017, according to a report today from the Congressional Budget Office. The CBO had projected when the law passed in 2010 that 32 million uninsured people would be on a health plan within a decade, and a year later raised its estimate to 34 million.