The US should split it's money system into an exclusive store of value and exclusive medium of exchange. The CDBC can have a negative interest rate, this means you only accept them if you want to actually buy something with them.

Because money is both a store of value and a medium of exchange, the government and central bank must constantly add more money to keep money in circulation. As that money gets saved, it stops circulating and the government must add even more money into the economy. Do you see the problem? You need money that can be saved (doesn't circulate) and you need money that circulates. Because it is mixed up in one currency, you must always create more but at the same time there is never enough.

If CBDCs have a negative interest rate, they will stay in circulation and we won't have to mess around with a constantly increasing money supply.

Switzerland has this separation with the WIR bank. They chose to inflate the WIR instead of the CHF.