First thing, you do not have to lose a vehicle in bankruptcy, if its chapter 13 then you will continue to pay it to the trustee, but probably at a better interest rate, the unsecured will be canceled. On chapter 7, I'm pretty sure you can reaffirm and keep that payment going for the auto. The credit cards( all of them) will get closed. But if its chapter 7 then you will be able to get another one not long after discharge.
Just not paying will likely result in adverse action by the card you keep open whether they would close it or reduce your limit each month until its nothing and then close it depends on the creditor.
Depending on the amounts and creditor of the other cards, you will likely get sued for the balances plus a bunch of other fees which will make the hole harder to get out of. Not to mention the endless collection calls.
I would suggest you spend some time over in the BK forum and look at options. Talk to a lawyer( talking does not cost) and look at your individual situation before going the not paying route. I was always hesitant to file bankruptcy and held on as long as I could only to still having to file. In hindsight I should have done it a lot sooner. Once you are in the situation of being overextended its hard to dig your way out, but it can be done with discipline and cutting out all extra expenses, even the ones you don't think are extra but really are.
If you default on all but one card, that card will most likely be closed because of your other delinquent accounts.
You can usually reaffirm your car in a BK.
is your total debt 15K owed? Is this just on the credit cards?
Although 15K is a lot to owe, I wouldn't file BK on it.
You might want to buckle down cut someexpenses , get a second job etc and try to pay down the debt .
35k car, 10k CC, 10k in loans
If $20k in debt is this problematic, driving a $35k car is very excessive. They are drowning because they are car poor.
I'd say to find a way out of the car and tackle things from there.