Also, presumably light has to travel farther in fiber because it's constantly bouncing off of walls vs. straight line travel?

I was going to dismiss it as insignificant, but if I read this right:

https://en.m.wikipedia.org/wiki/Total_internal_reflection

an angle higer than ~42 degrees seems to indicate roughly a 50% longer path?

That said, I wonder what the average "fractal dimension" of a city to city fiber link is - I suspect wavering path around buildings and along roads dominate the increase in path VS theoretical straight (curved along the earth) path?

Don't forget fiber splices for accidental cuts. Engineers have to try their best to match the existing refraction when splicing in the new patch. Tools help, but there's a lot of skill and craftsmanship there.

But a splice should either work, or not work? It is literally welding two glass strands into one?

A splice may or may not work, or something in between. The splice might cause enough attenuation that you go over your optical budget (signal strength and receiver sensitivity) so no link comes up. But it might come up just barely and then you may have some bad frames as a result.

This is true for multimode, anywhere outside short distances in datacenters you use singlemode where light does not bounce at an angle. A singlemode fiber acts as a waveguide, the signal travels in a single mode, this is mainly why it's good for longer distances, no modal dispersion.

That is not true. Single mode fiber definitely comes in at an angle and bounces off the cladding. You still have a cone of acceptance at play. You're confusing multiple terms and concepts here.

The point seemed more along the lines of "the ping is a function of the speed of light" to me, so not necessarily inaccurate. Although that does leave room for improvement like introducing a vacuum or making the lines more direct.