Agreed to all the above comments. I took out an annual excess policy this year with Questor which cost £50 and gave us a £50,000 excess on the care rental agreement plus other cover such as personal accident,road rage and car jacking !
It paid dividends straight away after someone drove into our hire car outside a restaurant in Spain and did a runner leaving us with an £800 repair bill which the insurance company paid immediately. As an aside we also complained to the Hertz Customer Care Service after the Spanish agent insisted our economy car we'd hired wasn't available and that the only alternative was a more expensive model. Being a late-night arrival with a tired family facing a two-hour drive to our villa I didn't argue and stumped up. Hertz refunded the difference immediately and apologised profusely.
There's some good information on this site here ( it doesn't have to be an Irish-based insurance company. ) You can request as much or as little extra excess insurance that you want for the US.
A word of warning about US car hire firms - some are notoriously crooked with agents on commission for selling as many extras as they can. We hired a car from Dollar at Orlando Sanford airport via a European broker and specifically requested no additional extras such as insurance excess and also the option of returning the vehicle with the tank full.
We weren't given a contract to sign, instead having to sign a hand-held device which then printed out a contract on the equivalent of a till receipt.They assured us we were not being charged for any extras and the credit card imprint they took was merely to cover any damages not covered by our annual excess policy.
On our return with the petrol tank filled we discovered not only had they already deducted for a full tank of gas ( at their more expensive prices ) but also added a roadside assistance service which we had not requested. The agents refused a refund.
We eventually got the $180 returned after much toing and froing with Dollar's US customer care service who rapidly settled when we told them we'd recorded all the initial conversation with the agent on an iphone and would be producing it in court.
We hadn't but it's a useful idea for the future and at all times check all the small print on the contract even if you're knackered after a transatlantic flight.
Two unfortunate car hire experiences in one year I know but US car hire companies, like Spanish ones, do not operate to the same standards of trust and honesty that we expect here.
Be vigilant at all times !