The connect IQ store won't let me download the new Amazon Music app because, it said, it was "not available in my country." I live in Ireland. Ireland is (for now at least) served by Amazon.co.uk. People in Ireland are able to avail of Prime memberships with almost everything that that includes: fast delivery, Prime Video, Prime Music, etc. so there's no reason we should be excluded from having this app.
I was evenutally able to download the app by geolocating to the UK using a VPN, but many Irish users won't be able to do that and shouldn't have to.
So, Garmin, I think you need to change the settings to allow users in Ireland to download the Amazon Music app (without having to use a VPN).