GM’s announcement of plant closures and layoffs Nov. 26 caught workers by surprise, but industry experts told Bloomberg Law that the cost-cutting measures are the latest signal of American automakers struggling with long-term viability.

Former General Motors Co. worker Tommy Wolikow was among those surprised by the announcement. He was laid off in January 2017 after experiencing other short layoffs in his time with GM. He’s waited for a chance to be rehired at the GM plant in Lordstown, Ohio,...