In many of these bank failures, the problem has been that they are holding very safe loans at an interest rate that is too low for today's environment. In practice, if they are allowed to survive until the loans mature, they will get all the principal back, so there won't be a realized loss there. Unfortunately, the rate is so low that if you need to sell the loan today it will be at a substantial discount to face value.
The losses that the banks would actually realize are that the cost of deposits have gone up: People want a higher interest rate on their deposits. If they don't get that rate, people pull their deposits, and banks aren't allowed to hold their safe loans to maturity because they need cash now.
Historically, rising rates have been good for banks because deposits are sticky and the banks can raise their customers' interest rates more slowly than they raise the rates on the loans they make. It seems that customers are more fickle now, and many banks weren't prepared for that.
The losses that the banks would actually realize are that the cost of deposits have gone up: People want a higher interest rate on their deposits. If they don't get that rate, people pull their deposits, and banks aren't allowed to hold their safe loans to maturity because they need cash now.
Historically, rising rates have been good for banks because deposits are sticky and the banks can raise their customers' interest rates more slowly than they raise the rates on the loans they make. It seems that customers are more fickle now, and many banks weren't prepared for that.