If you have a mailing list that is constrained to a few different countries and you are seeing opens in your campaign results that are from countries not included in that mailing list. An example of this is if you only send a specific campaign to companies in the UK, France and Spain but are seeing opens that are located in America.
There are various reasons this can happen but the main two are either the use of VPNs or from the email servers as they may be hosted in other locations. This is because the email server's security system could be opening the emails and checking links which would then mean that the location of the server is then recorded instead of the recipients actual location. A contact based in Spain could receive the email but because their email server has done a security check on the email, their location could then be recorded as the email server’s location which in this case is America.