Very short term interest rates in the US are set by the Fed, pretty much at will.

Under normal conditions, they have an extremely strong influence on medium term interest rates as well by convincing the market that they will keep short rates high(low) in the future, while will then raise(lower) medium terms rates.

If that proves inadequate, like it did after the crisis, the Fed can buy and sell bonds directly to move medium to long-term interest rates.

The Fed may have a historical preference for relying on the first mechanism alone, but through some combination of these techniques, they can set any interest rate to any reasonable value almost at will.