JavaScript’s time zones as a way to locate a user’s country

I need to determine a user’s country, and it doesn’t need to be super accurate (getting it right 90% of the time is probably enough). I realized the time zone returned by JavaScript could work.

Example:

console.log(Intl.DateTimeFormat().resolvedOptions().timeZone);

Will return America/Toronto or America/New_York, which can help me differentiate a Canadian from an American.

Sure I understand this is based on the user’s preferences, not its real location. But is there a huge pitfall I’m not seeing right now using this technic?