Hello,
Two possibilities:
This may be a region setting issue and not an actual change in country unless you truly went through all the steps necessary do that (and will have to reverse them to change back). This can sometimes happen if you find a link on the web that points to an app or a media item in another country's iTunes Store. Here's how you can correct this:
Sign out of the iTunes Store [ https://support.apple.com/HT203983 ] and sign in again to get the iTunes Store region to match the region to which your Apple ID country is set, as described in this post: https://discussions.apple.com/thread/250611340?answerId=251184940022#251184940022
1. Go to: Settings > Account > Media & Purchases > View Account > Country/Region
2. Make sure it is set to your normal country.
3. In the "Media & Purchases" menu, sign out and then sign in again.
The above is a simplified version of that in the support document 'Change your Apple ID country or region' ( https://support.apple.com/HT201389 ) except you shouldn't need to do the extra steps involved when you have done a true country change.
It is also possible that the item has been removed from the USA store since you last downloaded it. Legal - Apple Media Services - Apple - https://www.apple.com/legal/internet-services/itunes/us/terms.html - "DOWNLOADS You may be able to redownload previously acquired Content (“Redownload”) to your devices that are signed in with the same Apple ID (“Associated Devices”). You can see Content types available for Redownload in your Home Country at https://support.apple.com/HT204632. Content may not be available for Redownload if that Content is no longer offered on our Services." Always download everything to your computer and keep multiple backup copies on local storage.