[AngryParsley]

There's not much room for improvement. It's a little over 5000 miles from CA to the Netherlands, so light takes about 30ms to travel that far on a vacuum. That means a 60ms round trip minimum. Light in fiber goes at 0.6-0.7c, so the fastest round-trip you could have with a straight fiber line is 80ish milliseconds.

[sliverstorm]

Figure out how to make "fiber" that transmits light closer to c, perhaps? This of course would bring other challenges- the refractive index is part of why light stays "inside" fiber in the first place.

[kragen]

You can use a line of microwave towers, taking us back to the mechanical semaphore telegraphs from before Morse.