So, if buying American gov bonds is the safest way to lend money, it means that every single other form of loan must pay higher interest. Why? Because every other borrower is considered higher risk, and for me as a lender, I will not accept less interest for greater risk. So, if American bond interest goes up, all other loan interest (corporate bonds, bank loans, mortgages, credit cards, whatever) will organically go up, because everything must pay greater interest than American bonds to compensate for greater risk. This is simply a matter of supply & demand mechanics.