I doubt that your USAA insurance will cover you for any accident damage in Spain. Call them and confirm.
Our credit card does provide damage coverage, as long as that’s the card we use to pay for the rental. Do you have any cards that might? Call the number on the back of any cards to confirm that, too, as well as what foreign transaction fees (if any) that card would charge you for the rental.
In Norway in 2023, we got scratches on the car’s bumper, but were able to provide documentation to the credit card settlement department, and they reimbursed us 100% for the bodyshop costs that Hertz Norway claimed.
What did you do for Ireland? Coverage for collision damage, theft, plus windshield and/or tire damage? I know there are some rental companies (and consolidator companies like AutoEurope) that offer “zero deductible” (also known as “zero excess”) insurance for a (possibly hefty) fee, on top of the rental price. With that, you can essentially walk away from all damage and say, here’s your car, sorry, it got totaled, but I have full coverage, bye. If paying for that and not being a nervous wreck would let you enjoy your trip in peace, then that’s one option. But check with your credit cards first, and maybe USAA, too.