I think you have to be a bit careful about this. The type of cover discussed in the earlier thread seems to relate to personal accident and might also cover insurance excess ('deductibles') relating to an FBO's insurance cover on an aircraft that you rent in the US. But I don't think it covers your exposure to either the FBO if you damage his aircraft or your exposure to third parties if you crash on them or something. That's 'renters insurance' and it's a lot more expensive.
In my experience it is never clear what cover an FBO has anyway. I suspect some older aircraft don't have hull insurance at all. I suspect some (many) FBO's don't have cover in favour of the renter because some of them ask you to pay extra for it. Even if an aircraft is fully insured the FBO or his insurer might still choose to come after you. And of course if you damage it through some excluded action like landing on a gravel strip, or Sedona according to some operators, then the cover might not apply anyway.
Despite this I've never taken the renters insurance myself. I know and trust my FBO to be reasonable and know that he does have full hull insurance. I try as far as anyone can to avoid negligent acts, get agreement for unusal places and reckon in the limit I'd have to buy him a new plane. Frustratingly, he won't allow me to go to Baja California. Can't imagine why.
It's more difficult with the 3rd party liability. If I ran into an airliner the damages might be a lot more than the typical $1M mentioned (that's why even in the UK the MOD require £7M!). Generally the risk of crashing into people in the US is fairly small, comparable perhaps to tripping in a shopping mall and pushing someone down an escalator. I doubt that the FBO's insurance would cover me, though it might. It's a risk but so is life.