But after a weekend update to the social media platform X, it's now clear that the owners of these accounts, and many others, are located in regions such as South Asia, Africa and Eastern Europe.
Elon Musk's X, formerly Twitter, unveiled a feature on Saturday that lets users see where an account is based. Online sleuths and experts quickly found that many popular accounts posting in support of the MAGA movement to thousands or hundreds of thousands of followers, are based outside the United States - raising concerns about foreign influence on US politics.
Researchers at NewsGuard, a firm that tracks online misinformation, identified several popular accounts - purportedly run by Americans interested in politics - that were instead based in Eastern Europe, Asia or Africa.
The accounts were leading disseminators of some misleading and polarising claims about US politics, including ones that said Democrats bribed the moderators of a 2024 presidential debate.
Nikita Bier, X's head of product, announced on Saturday the social media platform is rolling out an "About This Account" tool allowing users to see the country or region where an account is based. To find an account's location, tap or click the signup date displayed on the profile.
"This is an important first step to securing the integrity of the global town square. We plan to provide many more ways for users to verify the authenticity of the content they see on X," Bier wrote.
In countries with punitive speech restrictions, a privacy tool on X lets account holders only show their region rather than a specific country. So instead of India, for instance, an account can say it is based in South Asia.
Bier said Sunday that after an update to the tool, it would 99.99 per cent accurate, though this could not be independently verified. Accounts, for instance, can use a virtual private network, or VPN, to mask their true location.
On some accounts, there's a notice saying the location data may not be accurate, either because the account uses a VPN or because some internet providers use proxies automatically, without action by the user.
"Location data will always be something to use with caution," said Alexios Mantzarlis, director of the Security, Trust, and Safety Initiative at Cornell Tech and a former director of the International Fact-Checking Network.
"Its usefulness probably peaks now that it was just exposed, and bad actors will adapt. Meta has had similar information for a while and no one would suggest that misinformation has been eliminated from Facebook because of it."