Amex said that liability was not included
Wow, I wish I would have known to pay with my card in the beginning. I am thinking that we are not going to be able to do the Amex insurance because of this.
First, let me say that I am not a lawyer, or an insurance underwriter, and they don't have Holiday Inn Express on Bonaire.
I believe that liability insurance is included in the car rental fee. What the add-on insurance give you is coverage for your vehicle. Liability insurance is the insurance that pays for damages you are responsible for, but not for your car. In the US, it is the car OWNER's responsibility to provide for liability insurance, not the driver/user/renter. I believe it is the same on Bonaire. Therefore, AMEX could not provide liability insurance for you as non-owner of the vehicle. If you are worried about the limits of liability insurance the rental car company carries, and whether it might be exhausted before the total claim is paid, I suggest you explore a Personal Umbrella Policy (PUP).
I had the unfortunate experience of seeing this tested last week. The driver (not me) of a rental truck (not from Buddy's, but that shouldn't matter), accidentally backed into a car passing behind while backing up in a parking lot. There was no light or horn signal from that car, but the driver was still responsible for putting a dent in the other car's door.
The police on Bonaire do not handle accidents like this. The insurance carriers hired a "middleman" investigator. He drives a well equipped van with something like "Caribbean Road Service" on the sides. I thought it was a repair facility. But this guy documents all accidents (at least those where no one is injured/death) for the insurance companies. Apparently the insurance companies have agreed to accept his documentation of the accident, and they then negotiate damages.
Back to the liability issue. I had taken the basic CDW (Collision Damage Waiver) on the vehicle, and the other driver was also listed as a driver on the policy. When we took the paperwork (given to us by the "middleman" to the rental agency the next day they were only interested in damage to their truck. Well, as you might imagine, the trucks big steel bumper fared much better than the thin sheet metal door - there was no damage. We were then told "no problems" over and over. When I returned the truck, they returned my open charge for the ~$500 deductible on the CWD. The damage will be paid by the rental truck company's liability insurance. This insurance is part of the base rental fee. Therefore, the additional insurance is covering your rental truck (think of it as collision and comprehensive type insurance vice liability on your own vehicle). The amount and type you want to purchase depends on the coverage and your risk tolerance. I believe the basic CDW covers only damages to the truck caused by a collision. Much like our collision insurance. The "Total" insurance covers things that even our collision coverage wouldn't. Like a blown out tire, crack windshield, or possibly damage due to theft or acts of god (hail in my neck of the woods). I don't have the AMEX card, but this should help narrow down the questions you might want to ask regarding what they cover.
BTW, as I mentioned in another post, Total Car Rental doesn't accept AMEX, and while at Island Car Rental (the company I used), I noticed that next door, AB Car Rental charges for using AMEX - I think it was $55, but it might have been $25. I assume this is because it is eating into their very profitable insurance income.
Also, I don't think you can get the Total insurance without the basic CDW. I have never seen it advertised as an incremental insurance. That is to say, I don't think you could use your AMEX for the basic CDW (if indeed that is what it is equivalent to) and then purchase incrementally the Total coverage difference on top.
If you have any specific questions, regarding my personal experience with auto insurance on Bonaire, just ask. I don't recall ever reading about someone who actually had to use the insurance in an collision where another vehicle was damaged. Of course, we all have read about damages not being covered by theft from vehicles at the dive sites.