Horrible cost on the first glance, but if you actually talk to doctors (my fiancee is one), you realize most of the system is under constant overload. If they have emergency call, it can be (and often is) something trivial, when taking a cab for 5% of the costs would be more appropriate. But you have tons of crazy people (not crazy enough to be in asylum, but enough to wreak havoc on everything and everybody around them) and hypochondriacs. Polytoxicomans that effectively can't be helped.
We're not talking about a drive by a specific vehicle, but locking of 2 highly trained professionals that can't be used for any other emergency, with vehicle full of life-saving equipment. Which can easily mean another ambulance has to come from afar if needed, which can be fatal/debilitating in number of cases.
So its not about US as much, its about making system effective, because resources (people, equipment, ambulances) are scarce and you need to prioritize, or people will die. These things can and should be improved, but until they are, doctors and everybody else need to work with what they have.