I have handled these types of cases for other people in your situation. This bill is just the tip of the iceberg. The insurance company usually settles the property damage with their insured right away. But the person driving that car may still be undergoing medical treatment. They have up to a year to use the PIP benefits from their policy to get medical treatment. It can go up to $15,000.00.
If you start paying the property damage, you can get hit later with the medical bills from the same insurance company. I have seen this happen to several people. It might even be a deliberate strategy that the insurance company is using to see if they can get some money out of you before you realize the bill is bigger and panic and file a bankruptcy. Only you don't get the money back that you already sent them.
On the flip side, they can't sue you for the property damage until they are ready to add in the medical (PIP) because they have to join all the related claims in one suit. Until they sue you, they don't really have any power to collect from you. You need to know what the total bill will be, including medical, to analyze the situation.
If you can't pay the bill and they sue and get a judgment, your license will be suspended until you pay the bill, which will then include court costs and will carry a 9% statutory interest rate. A bankruptcy at any point in the process will cut them off and make it possible for you to get your license again after the first year of suspension for driving without insurance has ended.
I would need more information to advise you as to whether a bankruptcy option is possible for you but from you statement that you can't afford $5,400.00, and that you couldn't afford insurance, I am guessing that you can probably do a bankruptcy without losing any of your personal property. My website link is below and on the page of articles and links you will see links on where you can read more about bankruptcy for free on the Oregon State Bar's website.