Prove it.
Two reasons. First, the US may have cutting edge technology/procedures. While the US may have, as of now, experimental procedures in almost all cases medical advancement is shared so there are few cases where that would apply.
Second, going on that assumption certain people will try anything to prevent death. We hear of celebrities going to foreign countries and trying all sorts of weird treatments when they are told there is nothing more that can be done in the US. Even a guy as smart as Steve Jobs decided on alternative therapy. Needless to say he didn't make it.
Unless a procedure is still in it's trial stage it's available to everyone under government medical. At least that's how it's run in Canada. Also, we have to remember how many people can afford experimental therapies/procedures. There is nothing forbidding someone to pay out of pocket for experimental care.