It's the one major health expense for which nearly all Americans are uninsured. The dilemma of paying for long-term care is likely to worsen now that the Obama administration pulled the plug on a program seen as a first step. The Community Living Assistance Services and Supports program, or CLASS, was included in the health overhaul law to provide basic long-term care insurance at an affordable cost. But financial problems dogged it from the outset.The irony, experts say, is that paying for long-term care is the kind of problem insurance should be able to solve. It has to do with the mathematics of risk.