Would a bad the rack and pinion cause the car to go off the road when driving over a bump?

I saw your other post that you are replacing the rack so depending on what you mean with everything else was replaced, the rack can cause this.

It is more likely to be a suspension component but if the steering darts when you hit a bump then that could be the rack having an issue with the air transfer tube that allows the air to move from side to side when you are steering.

If you have not replaced the tie rods, then I would suggest checking these and make sure you have not movement because that can cause it as well.

https://www.2carpros.com/articles/tie-rod-end-replacement

So let us know what you have replaced and if you are going to replace the rack, let us know what happens with that.

Thanks