Foreigners sell our stocks and bonds. Stocks and bonds go down. Dollar goes down. Interest rates go up. Stocks go down, more investors sell stocks and bonds, and other dollar assets. Dollar goes down. Economy goes down. Tax revenues go down. Ability to service debt goes down. Credit rating goes down. Causes even more foreigners to sell US assets. Stock market goes down, bonds go down, dollar goes down. Economy goes really down. Tax revenues go down. Debt is defaulted on. Get the picture?
Economics 101: The economy moves in a circular fashion.