This Element examines Secular Stagnation in the USA and responds to a recognised need for greater conceptual precision and analytical clarity regarding its nature and economic implications. Revisiting the contemporary economic debate, I propose a coherent reconceptualisation of Secular Stagnation grounded in long-run descriptive empirical evidence and an evolutionary theoretical framework. The analysis shows that stagnation should not be understood as a mere shortage of innovation or a transitory macroeconomic imbalance, but as a structural outcome of the interaction between technological change, demand dynamics, and selection mechanisms. Finally, I discuss how recent advances in automation technologies, such as Artificial Intelligence (AI), may either mitigate or reinforce Secular Stagnation, depending on how innovation policies and institutional settings shape the direction and diffusion of technological change in the US economy.