What does your reservation say about all the coverages? When you decline everything, in US reservation it says declined/declined/declined/declined. But on reservation in other countries, the declination may not be available, or some insurance may be included in the rate, etc. So it matters how all those lines about coverage read on your reservation and if there are any "fine print" notes on those.

I have never to Panama, but I have been to countries where it's impossible to decline all coverage: those "Super CDW" countries, where some uselessly small amount of CDW is automatically included in your rate, which precludes your credit card insurance working, and then you have to pay extra (only once your arrive!) to get the "super CDW" which almost (but still often not completely!) removes your collision liability.

Thus the collision insurance varies widely from country to country, and you have to research how it works in a particular country you're going to rent in.