Why Spain? How does Spain make this list?
The Spanish flu?
Spanish flu originated in Haskell County, Kansas, United States of America.
The American soldiers brought it into Europe. The reason it was called the "Spanish" flu was due to Spain's neutrality during WW1.
As a matter of fact, Kansas is only one of the hypothesis for the origin of the "Spanish flu", which, to this day, is still uncertain.
To complete what you said about why it was called "Spanish", the fact the Spanish was neutral and not at war meant that it was on of the only country to allow information about the disease and its impact to circulate freely, without the censorship and propaganda that applied in other countries. It means that, at first sight, it seemed that the disease was much worse in Spain than in other countries. Quite a lesson about how we consider the present disease... (Not that a country may want to pretend it did not start there...)