Smart speakers have proliferated globally, yet research on user privacy behaviours has largely overlooked how cultural contexts shape protection strategies. This PRISMA-guided systematic review analysed 14 empirical studies from five databases spanning the USA, UK, Netherlands, and Canada. Findings reveal significant cultural variations: users in highly individualistic cultures (USA, UK) favoured technical controls (e.g., muting, unplugging) with limited household privacy concern, while users in moderately individualistic cultures (Netherlands, Canada) adopted balanced strategies emphasising consent and collective negotiation. We propose the Cultural Privacy Protection Behaviour (CPPB) framework, extending Lutz and Newlands’ three-category model (technical, data-related, social behaviours) to incorporate cultural dimensions as a fourth category. We offer design implications for culturally-adaptive privacy interfaces, including culture-aware defaults and cross-cultural household support. This review demonstrates that effective smart speaker privacy design requires moving beyond universal solutions toward culturally-sensitive approaches.