The original study was of 65 undergrad psychologists at Cornell who got extra credit for participation. Probably a relatively narrow pool of personalities even in that region of the US.
In this study [1] the experiments were replicated in Hong Kong with 4034 high school students and in US with 95 students.
[1] "Why Do People Overestimate or Underestimate Their Abilities? A Cross-Culturally Valid Model of Cognitive and Motivational Processes in Self-Assessment Biases" http://journals.sagepub.com/doi/10.1177/0022022116661243 (paywalled)
Anyone know of replications with a wider pool?