> leaving a scattered few credit unions and smaller banks around

Your comment would imply a huge gap between this top tier of 3 banks and the rest of FDIC banking; there are quite a large number of large banking institutions available which are not as small as you've positioned them. https://www.mx.com/moneysummit/biggest-banks-by-asset-size-u...

(there are similarly very large Credit Unions such as NavyFederal with lots of asset: https://www.mx.com/moneysummit/biggest-us-credit-unions-by-a... )