Gen 4/5 had distributions locked to a specific language. The wondercards could be written in English for example, but it would have a language flag for that game. For example if WORLDS wanted to distribute the same wondercard in English to every language, there would be 7 wondercards, all in English, but with a language flag specific to the language it was distributing.
Gen 6/7 depends on the distribution method. The wondercards themselves are not region locked. Gen 6/7 has language limitation capabilities but as far as I am aware, it was never used. Serial code events are different. The serial code redemption itself is what determines the language/wondercard received (if applicable). Redemption of a serial code is region/language restricted. If a region supports a language, but the wondercard doesn't exist, then the user gets the region's default language (Japanese for Japan, Korean for Korea, and English everywhere else).
US - Restricted to NA (including SA) - English, French, Spanish - All other languages get English
EU - Restricted to EU Region - English, French, Spanish, German, Italian - All other languages get English
JP - Restricted to Japan Region - All languages get Japanese
KO - Restricted to Korean Region - All languages get Korean
HK/TW - Restricted to EU English, JP, and TW Regions - All languages get English
SEA - Restricted to US & JP - All languages get English
Sometimes HKTW and SEA are combined so it becomes All US, All EU, JP, and TW (I think Marshadow was like this?)