Would it be possible to offer both versions?

Or are the templates able to be altered easily by customers?

I would find US spelling in templates that I’m purchasing in Australia mildly annoying if I was unable to alter them, so I can understand that they may feel the same.

Having said that, all English speaking countries are expected to alter their spelling to fit the US but it is rarely reciprocated when they are selling to those same English speaking nations unless it is completely republished in the country of purchase. 🤷🏻‍♀️