Half of the reason the DonationInterface form settings exist is to steer donors to the right processor for a given country. The form chooser currently depends on banners or donatewiki doing the geolocation and sticking the country on the URL. When an email links directly to the form chooser and doesn't include a country, the form chooser is currently sending USD cc donors to Adyen, even though that form should only be preferred for donors in IL.