"U.S. bond yields have been rising since March due to fears of a bubble in Treasuries": the price of Treasuries is negatively correlated with the yield on Treasuries, the higher the price the lower the yield, and the lower the price the higher the yield, because yield = bond interest/bond price * 100%, which refers to the rate of return on a bond; in simple terms. Bond price is up and down, if you buy have $1000 treasury bonds, the annual interest rate is 5%, then the yield is 5%, if the price becomes $950, then the yield = 5%*1000/950*100% = 5.26%, then it is up, that is, the yield is negatively correlated with the bond price.
Because of the fear that the U.S. is going to continue to borrow money and continue to issue Treasuries, triggering a flood of Treasuries that are worthless, investors are just abandoning Treasuries, and the more people sell, the price of Treasuries goes down, which leads to higher yields.
Supplement:
1, all can, as long as the government feels the lack of money to use, can issue treasury bonds. Because money is needed to stimulate the economy.
2, the government has a treasury, which is the ministry of finance that manages a country's income and expenditures. Usually income is tax, expenditure is a lot, such as civil service salaries, national defense construction, people's education, health care, welfare, infrastructure, etc., a lot of need money; but taxes are limited, can not be arbitrarily increased tax levy, which will increase the cost of enterprises and individuals, so that their income and investment is reduced, is not conducive to the economy; so usually is the issuance of treasury bonds to borrow money; with the future tax revenue to return.