Similarly, the early Ellery Queen novels had a nationality in them:
The Roman Hat Mystery—1929
The French Powder Mystery—1930
The Dutch Shoe Mystery—1931
The Greek Coffin Mystery—1932
The Egyptian Cross Mystery—1932
The American Gun Mystery—1933
The Siamese Twin Mystery—1933
The Chinese Orange Mystery—1934
The Spanish Cape Mystery—1935
Their next novel, Halfway House was a change in how Queen was portrayed: they wanted to move on from the puzzle tales they had used previously. It was the last with the “Challenge for the Reader” gimmick and started concentrating more on character. They did suggest the title could have been The Swedish Match Mystery but clearly were giving up on the theme.
Later novels gave up on the nationality titling, so this fits the OP, too.