This meant that my android phone was a bit confused at times. When on mobile data the weather widget would default to showing me weather for random Czech cities, and search results would be Czech-localised. When on wifi connections, results were in English and Canada-localised, unless I bounced through a VPN exit node at home.
After 3-4 days, ads on Youtube started becoming Canada or Czechia-localised depending on if I was watching it via wifi or mobile data. It seems that google eventually decided that I was in Canada, continuing to play me Canadian ads even when I got home to Spain, on both wifi and mobile data. What was even stranger is that my partner started getting Canadian ads on youtube on her ipad too, which doesn't have any details about my google account (other than us living on the same internet connection). It took about 2 weeks for google to start playing us Spanish ads again.