So I have a diet pill website hosted in the US and aimed (mainly) at the US. I am in Australia however. Google seem to only give me traffic from Australia for search terms related to the pills. I have never had this problem with any other site but I don't use Adsense much. Anyone else experience this? Is there anyway around it (short of changing your country in adsense settings)?
I am running several multi language sites with adsense and can't confirm your observation. Nontheless ist's not easy to achieve similiar or equal rankings for the same search term on different Google country TLDs.
You can change preferred country settings in Google Webmasters Tools but nothing can be done in Adsense.