The survey was done of U.S. citizens. You can look up the survey on YouGov.com to see the population surveyed. The survey is titled “Democracy, Trump, and Musk”

Target population: U.S. Citizens, aged 18 and over.

Sampling method: Respondents were selected from YouGov’s opt-in panel to be representative of adult U.S. citizens.

As noted in their “about” page, YouGov does international research. https://today.yougov.com/about

With operations in the UK, the Americas, Europe, the Middle East, India and Asia Pacific, we have one of the world’s largest research networks.