Users in US are showing as located in Canada

We have had a few reports of users returning very specific Canadian locations even though they are clearly located in the US. It has occurred for users in California, Texas, and Arizona. It seems to be working fine for most users but for some the canadian location is returned and we are unable to figure out why. Below is the code we use to get the location, we have tried 2 methods, but neither seems to return US for all users. Is there something on an ISP level that could cause this?

$geo->country();
//TRYING WITH ENVIRONMENT VARIABLE instead
getenv(‘HTTP_GEOIP_COUNTRY_CODE’);