I was always wondering if every car around you had a Lidar, would these systems be confused by light emitted by other cars ?

In general, no. And to be clear, this is my general understanding and I don't have the time to look up the specifics, but I'm pretty sure lidar uses a "carrier wave" in much the same way old telephone modems did, or your IR remote for your TV. The carrier wave is how these sensors don't get confused. If you've ever been in traffic, and you get a stray, one off "YOURE TOO CLOSE TO SOMETHING" when you in fact aren't, it is because a carrier wave from another car happens to line up and you have a collision (pun intended).

two seconds of googling: https://www.digikey.com/en/maker/tutorials/2021/understandin...