Shopify shipping provinces/counties does not match google ones (and more problematic, existing ones)

Shopify Partner
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We're applying a shipping rate based on the location specified by the user
We use google autocomplete to help the user correctly provide his address

We do all this via the shopify storefront api


Problem is, the province returned by googlemaps does not match what shopify expect

Example : Catalunya ('Barcelona' area, Spain) is not in the list of the provinces under the spain country in the shopify admin when you select the spain country

So basically, the user can't update correctly its address for the concerned locations

Let's admit this is quite surprising, if not bogus; in any cases, returns a blocking issue
Catalunya exists for years, if not centuries
The problem occurs for Italy too, i haven't checked further but it might happen for others


Do someone have a workaround in mind ?