2005 Buick Rainier - What did I break!?

I have a 2005 Buick Rainier I was driving it and getting ready to make a turn at a very slow rate of speed and I accidentally went from drive to neutral It made a sudden stop I put it in to park turned it off then turned it off then restarted it now it’s running rough what damage could I have caused?

Hard to say given your description. Why not take it to your local independent auto repair shop and let them take a look. Eliminates the guessing game.

No idea what’s causing that. The only clue I can provide is that something similar happened to my Corolla one time. I was testing the crank function without the ignition system turned on. The engine sort of gave a minor hick-up, which I presume was gasoline igniting without a spark, like a diesel engine. I didn’t think anything of it, but when I started the engine the normal way it no longer ran perfectly like it had been before, Instead it ran poorly and idled very uneven, with the idle rpm going up and down by hundreds of rpms for no apparent reason. The problem turned out to be that the “hiccup” somehow upset the idle air control gadget. How that happened, no idea. But suggest to ask your shop to check everything involved with the idle air control function.