Your original supposition does NOT make for a very good way to analyse a bank for many reasons.
One is that in US banking not all deposit accounts are the same to a bank,
A Demand Deposit Account (a DDA) things like personal savings, checking, etc - all require the bank keep almost 100% of that amount in cash reserves (for lack of a better term). The need for that is a big reason for our banking system and the interbank rates, etc. where they lend money to each other for (generally very short_ periods.
Other deposit accounts - like a Certificate of Deposit (CD) have specific time frames before the bank is expected to need to have the cash - so say one that is for 36 months requires much more kept on reserve than one due in 10 years. Each type of those offering has a different amount required for the bank to keep in cash (and the difference between having to keep cash or not is a matter of leverage on the return - a BIG difference in profitability). In fact on a loan given when rates were lower to the customer than they are now to the banks it could actually cost them to maintain the cash reserve, even though the interest spread may be great in writing.
Also, the way a portfolio of loans (say mortgages) gas many ways it may be handled, not relative to the difference between the rate on the amount loaned and the cost of the funds NOW. (Many banks main involvement with mortgages for example is they only SERVICE (accept and process the payments) for mortgage loans others actually own. For this they make a fixed fee from the lender. (And consider, if the bank you look at has someone else service its loans - then THEY are actually making much less than the interest spread noted - and less than one that services it themself...albeit they don't have the cost of the service function).
There are many other reasons you should learn more about the operations of the many different types of chartered banks in the US and the system they operate in than to think the difference between the (many) rates they charge for a borrowing and the many different rates they pay for different deposit vehicles (all constantly changing) would actually indicate profitability.