Yes, failure to signal is a traffic violation. At least everywhere I've lived/traveled in the US. It's also a rather convenient excuse for police to "randomly"

Yes, failure to signal is a traffic violation. At least everywhere I've lived/traveled in the US. It's also a rather convenient excuse for police to "randomly" pull you over (I've been pulled over by Chicago PD for not signaling for a lane change, despite actually having done so).