Correct, the US Federal Reserve is a Proof of Stake system. Members earn 6% dividends for the last 100 years, and this was to entice them to join the system at all. Just pointing out that the idea of an omnipotent US government is a fairly new concept, and it must incentivize and entice people to join its payment network as opposed to other private ones.

The private networks for final settlement are becoming more interesting to market participants. And they are also aiming for distributed (sharded) proof of stake.