Social security numbers being involved in a breach does not mean that the breach only affects Americans. Some records might not have an equivalent ID number associated with them at all, and some records could have similar ID numbers from other countries. They also list current address as part of the data leaked but the fact many people don't have a current address didn't seem to cause you any confusion. The original source lists "information about relatives", if that was in this title would you have assumed only people with living relatives were included?

"I didn't read the article" is a poor excuse when you're commenting on the believability of the article. What happened here is you saw an article, immediately assumed it was about the US, realised that doesn't make any sense, then dismissed the article without even bothering to check because the title doesn't fit the US exclusively. It's crazy to me that you wouldn't even consider the fact it's not an exclusively US-based leak.