They do have around that much.....It's the second biggest bank in United States.
Their size relative to others in the US is completely irrelevant. Their market cap and book value is about 150BB. If they were ordered to pay 100BB or probably even 50BB, they would just declare bankruptcy. Simple as that. You don't have to be insolvent to declare bankruptcy. Yes they have 600BB in cash, but that cash is tied to leveraged assets, thus you take away $1 of their cash, you're taking away $5-10 of their assets.
You should google "bank balance sheet" and "tier one capital ratio".