American Robotics, a Waltham-based drone startup, laid off approximately 50 employees last week, representing a significant 65 percent of its staff. The layoffs are part of a broader trend affecting the local tech sector in early 2023, driven by economic slowdowns, uncertain market conditions, and adjustments following periods of aggressive hiring. The company's parent, Ondas Holdings, cited the challenging economic climate and the need to accelerate integration with another drone firm, Airobotics, as key factors. This move reflects the industry's shift toward more measured growth amidst ongoing market volatility.