> Social Security existence is based on the state ability to extract taxes, and voters rejecting candidates who want to dismantle it.

You need to watch the discussions around "entitlement reforms" that's being promoted currently. Voters can't reject candidates after the fact, who won't seek re-election after passing (or being the lightning-rod of) unpopular legislation, opting instead for cushy "jobs" in the industry they legislated in favor of against their consituents interests.

>>401k depends on stock market being up in the critical time you need it.

If your portfolio allocation is incorrect, sure. But by the time people get close to retirement, most of their investments should be in bonds, which are quite insulated from the ups and downs of the stock market.

What do you do when the stock market collapses as you start moving into bonds?

If you want to take an ultra-conservative approach, then 7 years from retirement, transfer 7 years worth of expected draws against your portfolio into bonds. If the market crashes the day before the "7 years from retirement" point, then wait 7 years to make that move into bonds and do it just when you retire.

If things are in such horrible shape that the market fails to recover over any given 7-year period of time, expect shotgun shells and canned food to be the new currency anyway.

That’s something you do by degrees over years. A couple years’ blip isn’t going to hurt that much.

Collecting a growing pot of tax revenue from a shrinking pool of workers will not be without challenges. Emigration seems likely, although I suppose the elderly majority can then vote in an exit visa scheme.