need to dispel some myths,
there is no such thing as "the best healthcare on earth".
Until a few years ago, many of the most advanced techniques were being pioneered in the US, but not all. Barnard, who became the world's first superstar surgeon, did his famous first heart transplant at Groote Schuur Hospital, in f* South Africa. In 1967.
And, there is no exact idea of what "best healthcare" means. The most difficult, most advanced procedures are done by very talented individuals, leaders of their field, some of which are in the US, some of which are not. Japan, Dubai, Israel, have phenomenal medicine, the UAE has some of the world's most modern hospitals. Various european countries have talented specialists of note that you may need to fly to, from the US, if your illness requires their specific skills. Italy isn't exactly a world leader, and yet we have extremely advanced specialists in all fields of science and medicine.
Also, many countries manage to do a lot more with their healthcare, than the US does. Once cannot just brush away this by saying "it's here, but you gotta pay for it". And again, while some countries with socialized healthcare tend to have longer wait-times, they also all have private clinics, if you are so inclined. There isn't anything a US private clinic can do, that a equally-private yet less expensive Swiss clinic cannot do, in the same time, with the same level of accuracy.
Finally, there's bad hospitals and bad doctors in the US as well. Obviously it's no comparison to ghastly places like Barbados or Ghana, but they are not substantially better than their counterparts in other places. Lol, Thailand has facilities as advanced as the US have, this isn't the 80s anymore.
In regards to the OP, we've never managed to negotiate down an ambulance transfer. Hospital invoices, those we get them reduced all the time, but ambulances we always wind up paying the full amount. I don't think ambulances need to itemize, or otherwise explain their charges, so they get free pass to charge you whatever they feel like.