In addition to what Zas has said, I'd like to note that this:
is not true.
Consider the scenario that a US product shares a barcode with an EU product (this condition may not even be necessary for): Amazon US would then list a back cover scan from a product (an EU release) that Amazon US doesn't actually sell.
And it's very easy to tell a major record company's US release from an EU release.
This means it's almost always an error to merge a US CD with an EU CD.