Background: Colorectal cancer screening has been shown effective at reducing stage at presentation, but there is differential uptake of screening based on insurance status. We sought to determine the population-level effect of Medicare and screening guidelines on colorectal screening by race and region. Methods: Data on Black and white patients with colorectal cancer were obtained from the SEER database. Regression discontinuity was used to assess the causal effect of near-universal health insurance (represented by age 65) and United States Preventive Services Task Force guidelines (age 50) on the proportion of people presenting at advanced stage. This was stratified by race and region. Results: In the Southern United States, Black patients saw a significant decrease in advanced stage at presentation at age 65 (coefficient -0.12, p = 0.003), while white patients did not (coefficient -0.03, p = 0.09). At age 50, neither Black (coefficient 0.09, p = 0.10) nor white patients (coefficient -0.04, p = 0.1) saw a significant decrease in advanced stage. In the Western U.S., neither Black (coefficient 0.02, p = 0.72) or white patients (coefficient -0.02, p = 0.09) saw a significant decrease in advanced stage at age 65; however, both Black (coefficient -0.20, p = 0.008) and white patients (coefficient -0.05, p = 0.03) saw a significant decrease at age 50. Conclusions: Our data highlight the significant impact that near-universal insurance has on reducing colorectal cancer stage at presentation in areas with poor baseline insurance coverage, particularly for Black patients. To reduce disparities in advanced stage at presentation for colorectal cancer, state-level insurance coverage should be addressed.