As far as I am aware, all that matters is that the serial
number you use corresponds to the language version of your Adobe
software. A serial number for an English-language version will not
function with an application in (say) French.
Your geographical location should not be taken into account.
If you are buying Adobe software outside the US, you are
likely to get a better price by going through a non-Adobe vendor.
My understanding is that Adobe is required to overprice its
software deliberately outside the US, in order to avoid being seen
as competition to local vendors.