Who is going to buy them? Most US citizens have less than a month's worth of income in their savings account. I'd be surprised if they enough confidence in their own income to tie even half of that up in war bonds.
Many (most?) Americans have no savings account. Not because they are poor but because a savings account is largely an obsolete anachronism. The common tactic of conflating "savings" with "having a savings account" is intentionally misleading.
Per the US government, the median US household has $1000/month they could invest after all ordinary expenses.
Perhaps we'll be forced to accept that we cannot continue to have "endless growth" with a declining workforce. The cost of Labor is going to go up at all levels, and that will mean smaller profits and more inflation until things stabilize and enough of us are incentivized to do productive work.
Per the US government, the median US household has $1000/month they could invest after all ordinary expenses.