The short answer - impossible to be sure.
The longer answer - research and experience. 
There are a few pointers on a disc and packaging as to the Market that disc was aimed at. For example, the ones you are describing sound like USA discs to me. Or maybe USA + Canada. (I’d have to see the images/examples).
Or, more likely, you have a lot of “Worldwide” releases as many of the discs I have worked on with you previously would have been sold direct from the artist’s own website. And if there is Worldwide shipping, then you have a worldwide release. He wants to spread The Word.
Discogs is not ideal for these kinds of Releases as there are not enough collectors of them on there. Yet for some artists it can be an excellent resource. Just depends who has added the data. (Wikipedia is a similar one for being hit n miss depending on the interests of the contributors)
You need to “Find the geeks” who have produced a catalogue. Some of the artists I follow pop up on fan created websites who have been documenting the details over the decades. Or the band themselves have some of their history. (Though it is a little funny as to how often the band themselves haven’t a clue as to what was released when 
)
For the large artists on big name labels it is very common to have a CD printed in one country, paperwork printed in a different country, and then sold on a totally different continent. I bought a CD New from Amazon in the UK - but it was actually produced for the Argentine market. But as Amazon are huge, they just moved stock from South America over to Europe and sent me one of those disks. This means your place of purchase isn’t enough either.
I have a number of CDs in my collection that were “Made in France”. These are from obscure punk bands which I know would only have released a small number of these albums in the UK. So they are UK releases, but that is only due to my own knowledge.
And as to DATE of release - close to impossible to nail down. Usually you only see copyright dates on a disc. A first issue of a release may well be the same year… but reissues then get very messy to nail down dates.
The best source is the artist themselves. There is more chance of getting dates by digging into the artists old sites, old promotion material, the artists’ own pages. Find interviews with the guy when he is talking about his music. Talking about his works. And next up, look for the fans talking about the artists. Or the pages created by fans. THAT is the most reliable place to go.
Even the handful of discs I have helped you with I could see an Australian artist starting with self released discs. Therefore Australian. He then goes off to Nashville and release stuff there making USA releases.
Trying to nail down dates can be comical. In the past 18 months I have learnt far too much about the small details of music production, CD presses, glass mastering, and all kinds of weird little bits of knowledge that surely only the truly mad would care about. 
But then I love a bit of research and daft details.
Much of this comes down to a level of proof. How SURE are you about the information? MB’s guidelines.
(It will never(?) be before the copyright date though, so that’s at least something…)
This.