This just seems like hand-wringing for the pitiful state of the rail system in the USA. A country can have many dense population centres separated by large distances, making HSR viable and worthwhile, but still have low population density overall - just like the USA. The only real obstacle is political will/public support.

Western China has around half the population density of the USA but is already served by a 1,900km HSR line.

My understanding is that metallic spherules from iron meteorites would be expected to include nickel. The absence of nickel in iron containing spherules like these would usually indicate a non-natural source i.e. human technology. The speed and trajectory of the meteor which may be the source, however, indicates an interstellar origin.

I believe that initial analyses of these spherules has revealed an absence of nickel.

The spherules were recovered from areas in the expected debris zone; none were recovered from the surrounding, control zones.