Why doesnt everyone qualify for the same interest rate when they apply for a loan? What are some of the factors that affect the rate of interest a borrower has to pay?

The U.S. national debt has recently surpassed $22 trillion (see the attached file). How do you feel the current government deficits and increase in the national debt will affect interest rates and the economy in the future? Are the government's actions the correct way to keep the economy going?