One way to do that is to raise the age of eligibility to at least 70 and then progressively increase it to track with life expectancy. This won’t be popular, but Americans’ dependency on government programs is less entrenched than that of Europeans.
The problem with this, of course, is that many elderly people find themselves squeezed out of jobs when they reach their late 50s or early 60s. I have a relative aged 64 who was recently laid off in a cost-saving measure, and the odds of her finding a new job are practically nil. It's going to be hard enough for her to survive until Medicaid kicks in at 65. Andrew himself has published emails from people this age bemoaning the lack of job opportunities for folks their age. Raising the retirement age would only exacerbate this problem.