Either way you look at it you're involving time travel through the normal universe.

For someone 20 light years away to click a button and a laser appear at a spot next to you simultaneously. I mean, whew. There's so many things that have to be accounted for that it boggles the mind.

1. The universe is spinning.
2. The galaxy is spinning
3. The solar system is spinning
4. The planet is spinning.

All together you are moving hundreds of thousands of miles an hour. Over 20 years that's trillions upon trillions of miles.

This laser would have to compensate for the universal drift of 2 points nineteen sextillion meters apart over the course of 20 years.

That's aside from the point.

We are dealing with things that are faster than the speed of spacetime. (space is time, time is space)

So, what would happen is you would click the button, and the laser would arrive at its intended destination 20 light years away simultaneously.

Then, the universe will start to catch up to the lasers pre-afterimage. (I can't think of a better term for this, I'll try to explain. You're with the laser at Point A. Destination is Point C. The Point B is the space and time between Point A and Point C. After the laser instantly jumps from Point A to Point C, the universe must still inexorably traverse Point B, during which it will encounter, in its future, the past afterimages of your laser, a.k.a its pre-afterimage.)

That is what I mean by the laser traveling into the past. Even though it's the same point in relative time between Point A and Point C, the laser, assuming that it is following some version of universal law, must still traverse the distance between the two points. If it did it faster than the universe can, that's fine, the universe will still commute that time distance either way.

From the point of view of Point C, the laser will appear and then recess back towards Point A over the course of the next 20 years. (This has to happen because the universe moves at the speed of light even if something else within it did not).

From the point of view of Point A, 20 years ago a laser of some intensity was fired at it and hit it the moment the button was pushed.

Both of these things are true because the speed of light was broken by your magical laser.

During the universe's commuting of that time distance, interesting things will happen.

When I was talking about the laser tsunami (and thank you for creating an opportunity for me to earnestly write the phrase "laser tsunami" twice in my lifetime) that is talking about what must inexorably happen on the other side of Point A or Point C temporally. For Point C, not much, a little flash of light. For Point A, either some really pretty light shows or total universal destruction. Sure, whatever.

But no matter how fast the laser moved, the universe must still cross the length of Point B, and as it does so (since we are moving in linear time) the universe will experience either essentially negligible effects (in the case of the 2 happier endings I presupposed in my last post) or it will undergo catastrophic alterations as it reacts to more energy than exists within itself ripping across 20 light years of distance in an infinitely short amount of time.

Light doesn't have mass but it does have energy. Energy is mass. That will have an effect on the universe whether you want it to or not.

Space and time are the same thing. 20 light years of distance is therefore 20 years of temporal distance at least from the inside of this universe.

Point C by all accounts must therefore be 20 years in the past from Point A in order for a laser from Point A to hit Point C at the time the laser is fired from Point A. This is despite the fact that they are currently at the same time frame in the temporal view. (That means that when you have a faster than light anything, everything that it can reach at faster than light speeds must be in the past even though they are both now).

If it wasn't, you would miss the shot because where you pointed the laser on Point C would be where Point C was 20 years ago, hundreds of trillions of miles away from where it would be right now.