U.S. banks are sitting on $326.7 billion in unrealized losses right now. That number has grown for two straight quarters.

These are paper losses on bonds and securities they bought when rates were near zero. Now rates are higher, those assets are worth less. Banks don't have to realize the loss unless they sell, but it's still real risk on the balance sheet.

This is the same dynamic that broke Silicon Valley Bank. Most banks are fine because they can hold to maturity, but it shows how sensitive the system is to rate moves. If deposit flight picks up or liquidity tightens, some smaller banks could face real pressure.

Watch the smaller regionals. The big guys can absorb this. The little ones can't.