Purchases Unavailable despite now being available for purchase in AppleTV App

The purchases are tied to your ID and location. If providers remove content, makes changes or you move locations there will be content that is then unavailable in the cloud. It is always recommended to download and backup purchases so you have access to the tangible item, which is what you paid for. There is no guarantee for cloud access and it is covered in the terms.

Any content from the iTunes Store has a regional license. You purchase the right to use/view/stream the content in the country of residence where the purchase was made.

Purchases from the US are not available in Switzerland as already purchased items. The same title may be available, but it won’t be recognized as a title that you already purchased. You may have to re-purchase items in the new region, as a new item. There may be content differences: subtitles and/or dubbed audio tracks.

All purchases are tied to the Apple ID account, not to a specific device. You can’t “move purchases to Apple TV”.

I was under the impression that downloading the content was also against the terms.

No, for iTunes Store purchases, it is actually advised to download content before changing the region of your Apple ID.

Change your Apple ID country or region - Apple Support

“To make sure that you can access your previous purchases in your new country or region, redownload your previous purchases on every device on which you might want to view the purchase before you change your country or region.”

Additionally it does not appear that an AppleTV has a facility to download the content permanently.

Correct. Apple TV only buffers small segments in order to provide smooth playback. It is a streaming device.

But, in theory if I can get my family in the US to login for me they should be able to download content and send it for us?

If you still have a different US Apple ID, then the content should still be accessible on that account. It is the listed billing address of the Apple ID that matters, not so much where the downloading person is physically located.

Have to say though, it’s awfully convenient for Apple.

It sure is inconvenient for people that emigrate.