I searched this question here and found this answer and this answer but neither works for me.
I set US timezone in Windows, start VPN with a US public ip address, clear all cookies/cache/history, before starting my desktop browser(firefox with restrictingfingerprint enabled). But when visiting google.com, it still redirects to country-specific google domain and my real location(country and city) is displayed below the search result page. I even pass all the leak tests mentioned in the answer of How does my browser know my location when I am on VPN?
No mobile/wireless/wifi is used. Of course I am not logging in google account. How on earth does google know my location?