If you think US Social Security is a "Ponzi scheme" (it is not, by definition), then do you also think all other highly developed nations are running Ponzi schemes because their national pension is paid from current accounts? Something that I see rarely discussed: Most national pension schemes need means testing. If you already have reasonably large savings, investments, or passive income, then you don't need the full amount of national pension. You can receive less. The remaining portion can be redirect to those in greater need. One thing we have learned in economics in the last 10 years, when poorer people receive direct cash payments from govt's, they spend it into the economy as a much greater portion than those wealthier.

Also, the US has 401(k) savings plans. It is pretty similar to Kiwisave.