The federal reserve is the US printing press, but can only loan money, mostly for a maximum of 90 days.
https://www.federalreserve.gov/regreform/discount-window.htm
It sets short-term interest rates by setting the interest rate it demands on those short term loans.
When the US _borrows_ money, the interest rate is set via auction. "This bond will pay $1000 in 30 years, how much will you give me for it today?"
The government would _like_ the rate it lends money at and borrows money at to be correlated but they can diverge a lot.
