Google said by the end of this month you will need to control global product availability in your product feed. You can apply the shipping attribute to products directly in the feed or specify countries by using the “additional countries” feature. This applies to both Shopping ads and free listings, Google said.
A month ago we reported about using the feed to exclude countries as an FYI but now Google said this is coming by the end of this month.
In the past, there were two ways for products to become available in multiple countries. You could specify countries through shipping settings (either by creating an account-level shipping service or by applying the shipping attribute to individual products), or you could specify countries in your Shopping ads feed (either as the country of sale, or by using the “additional countries” feature).
Google is pre-selecting countries in your feed to configure as “additional countries” of sale starting the week of September 14, 2020. For most merchants, this doesn’t change the availability of your products across countries. Up until September 30, 2020, Google will use Merchant Center shipping settings to determine additional countries for your product data. After this time, further country selection changes can and will be configured on the feed or product level. Your product-level shipping attributes will continue to apply.
There are a lot more details on this change over here.
Forum discussion at Twitter.