Airbag light on and horn not working

The only way to know if the service caused the problem is to know why you needed the alignment. Were worn parts replaced, and if so, which ones?

Given your description of the symptoms, it's a pretty good bet the "clock spring" is broken. That is a wound-up ribbon cable in a plastic housing under the steering wheel. It's not uncommon for that cable to break at high mileage, and it could be a coincidence that just at the time it was ready to break, the vehicle was in the shop for an alignment. As for the alignment itself, there is no way that can cause the clock spring to break. The only thing we can do is if the steering shaft has to be disconnected, for example, to replace the rack and pinion steering gear or a worn universal joint in that shaft, and we rotate the steering wheel one or more turns during that time the shaft is disconnected, it puts that clock spring off-center by one or more turns. That cable is only long enough to handle the steering system being turned from full-left to full-right, and little more. When the steering wheel is turned one or more turns, once the shaft is reconnected, when you turn the steering wheel fully one way, that cable will be too short and will be torn loose, or it will unwind too far the other way and fold over on itself. That has to occur multiple times, typically over days or weeks, then the cable will snap on that end.

If no other repairs involved disconnecting the steering shaft, I can't think of anything related to aligning the vehicle that would have caused the failure other than bad timing.