Millions of Americans who are already struggling with the cost of living could eventually feel the effects of persistently high debt as US gross federal debt surpassed $40 trillion on Wednesday and economists and think tanks warned that it's a "huge burden" that could drive up interest rates, inflation and borrowing costs.

The federal debt reached $40 trillion as the government adds red ink at a rapid rate. That's leading nervous investors to demand higher interest rates —pushing up borrowing costs…

The United States is digging itself into an ever-deeper debt hole.