Rentalcars.com will give you CDW insurance with their rentals, even in the USA. Then all you need is the excess insurance. The 15,000HKD covered by CX insurance will get close enough to the excess cover required. I never hire directly through the rental company when in the USA. They are a total rip off. once, a one day rental for $40 dollars truned into a $120 one when I returned the car, as there were heaps of hidden charges, like one day rental, drop off fees, hideen insurances fees that I had to have, on top of that, they charge tax on top of other taxes!. The good thing of going through an web company, is that you usually pay upfront. No hidden extras when you collect the car.