Banks in the U.S. that failed in the past two years were in far worse shape than those that collapsed during the industry's last crisis, a looming problem for the government agency charged with insuring deposits.

At three of the five banks that failed Friday, increasing the total to 77 so far this year, the financial hit to the agency's deposit-insurance fund is expected by the Federal Deposit Insurance Corp. to be about 50% of their assets.

The...