SIPC insurance. More likely ML will be spun off or sold for BAC to meet the new stress tests coming next year.
I will give you the real reality. your pension will be seized by the US government if BAC fails and Obama is reelected.
In reality, no major bank will go bankrupt in your lifetime. These things will just get bailout money or be backstopped by the governments of whatever country they are in. They are just too big to fail. Countries can fail but the banks will not.