Welcome to WebmasterWorld Guest from 220.127.116.11
https://www.google.com/?gl=usworks with or without Incognito mode as long as Location Tracking is Off (which is my default in all browsers anyway). In Chrome:
https://www.google.com/?gl=usstill gives me a lot of UK Ads at the top of results, which implies that it is the location setting, not Incognito mode, that makes the difference.
https://www.google.com/search?gl=usor any other country code, definitely works if you can't do it any other way, and if you haven't done so then I recommend you give it a try, if only to see messages like: