I acquired a website that is hosted outside of the United States. It mentions the United States all around the adsense code, service but the home page keeps showing out-of-country ads. These ads are targeting the country where the website is hosted, but there is no mention or link to this country anywhere in the source code of the webpage. Even stranger, this only happens on the home page even though all pages are dynamic and use the same code. I know adsense targets ads based on the IP of the user, but I never heard of the host playing a role in which ads are shown. Can anyone confirm this or rule this out?
I can't confirm it for sure but I have read of similar situations to your own, however, you need to make certain that it isn't your own search history that is triggering the ads if, for example, you have been searching a lot of international type sites yourself. If you think it is entirely down to host location then all you need to is transfer hosting to a US based one if that's your target audience, and redirect the nameservers on your domain name to point to your new host.
Although I don't tend to believe this. You can PM me the site and I will let you know if it targets me. I have many US hosted sites that show Irish ads when I visit them here and show US ads when I am visiting family. I also have a lot of UK hosted sites and have never seen that over ride my local settings.