That doesn't make sense, unless I'm misunderstanding you. In different countries you'll be using different satellites.
However, the iPhone uses more than just GPS - it uses cell sites and WiFi, too. I've sometimes found that it's more accurate if I go into airplane mode, which shuts down everything other than GPS-monitoring.
This just gives more evidence to someone else's comment earlier in the thread that said the Intel modem is interfering with the GPS.