In this study, we analyzed and compared reasoning and proving opportunities in geometry lessons from American standard-based textbooks and Korean textbooks to understand how these textbooks provide student opportunities to engage in reasoning and proving activities. Overall, around 40% of exercise problems in Core Plus Mathematics Project (CPMP) ask for reasoning and proving activities while 20% of exercise problems in Korean textbooks are about reasoning and proving activities. One of the major findings is that Korean and CPMP students have different opportunities in learning geometry. It may be interesting to investigate geometric reasoning and proving performance of Korean and CPMP students to see how textbooks influence their learning.