Questions for Santa.

[Fireball]

Relativistic flight inside the earth's atmosphere would be a rather dramatic event.

Also, the flight path would necessarily be curved and bremsstrahlung radiation would be quite directional and possibly even randomly focused in places so in addition to the staggering devastation expected from straight line paths over the earth's surface, the bremsstrahlung radiation would create spots and streaks of enhanced damage scattered all about.  I'd wonder if brilliant flashes of radiation might even impinge on the moon and damage it's surface too.

And it's a given, aliens watching the earth from afar would notice something BIG had occurred!

Cosmic rays and neutrinos can get away with it, as well as some other particles. But an ensemble of that many moles of material would indeed make a mess of things.