Am I right in thinking that these are only optional extras on the U.S. site because most Americans have the necessary coverage through their credit card, whereas most Europeans don't?
Yes, that is exactly correct.
How then do American car rental counters get their commission from "normal" Americans?
Well no one has ever called me normal, but I am an American, so I feel qualified to answer. First off, Hertz, Avis, or whoever is charging you for the use of the car, so there is profit in that right there. They also buy the cars at a steep discount and then sell them on the open market after they have reached their useful life, so that is part of the business as well.
Additionally, they often give leisure travelers (the ones who are not signed up for frequent renter programs that let you skip the counter) the hard sell on insurance telling them that they may not be fully covered by their credit card and/or personal auto policy. They convince a fair number of people to buy additional coverage at the counter, thus inflating their profits. Also keep in mind that credit cards do NOT provide liabilty covergage, so unless the renter owns an automobile and has their own auto insurance (or a non-owner policy which is rare), they would need to purchaese liability coverage from the rental company to be covered for damage or injuries they cause to other people or property.
Last, the rental company have all sorts of
other add-ons to sell you like upgrades,
GPS,
prepaid gas,
additional drivers,
roadside assistance, SiriusXM radio, etc.
You can read more about
rental insurance coverage in our blog here.