This review paper examines the theoretical perspectives on cybersecurity challenges facing critical water infrastructure, with a focus on comparative insights from Africa and the United States. By exploring foundational theories of risk management, resilience, and deterrence, the paper delineates how these concepts are applied and adapted to address the cybersecurity needs of critical water systems within the distinct contexts of the two regions. The analysis identifies common challenges such as malware attacks, system vulnerabilities, human factors, and how regional differences influence technological infrastructure, regulatory environments, and cyber threat landscapes. Through a comparative analysis, the paper highlights lessons learned and best practices from both regions, emphasizing the importance of capacity building, comprehensive risk management, and the role of public-private partnerships. The paper concludes with a call for future research to develop adaptable theoretical models that address different regions' unique cybersecurity challenges, underlining theoretical understanding's critical role in enhancing the global resilience of critical water infrastructure against cyber threats.