The two Swedish officials are introduced as "Interpol detectives". The Interpol has no investigative authority and its objective is to facilitate international cooperation of law enforcement. Any case of stolen art between two countries would be dealt with at the diplomatic and government level (typically, Foreign Ministries).
Captain Holt wears his Commendation breast bar above his World Trade Center Breast Bar. When the WTC bar is worn, it is worn above all other medals, but below the American Flag bar.
Although his face is not visible, when Jake (Andy Samberg) holds up the diamond necklace in the precinct after catching the perp, he says the name of the necklace in Swedish. It is clearly not his real voice, and has been dubbed by a Swedish speaker.
When trying to teach Gina about Astronomy, Amy mentions that Star Wars has an error regarding parsecs. In fact, in the Star Wars universe (Solo: 2018) it is clear that when Han Solo is talking about the Kessel Run, he is talking about how short the distance he had to travel was not how quickly he did the run. By going into the maelstrom and off the set path, Han was effectively going off-road to take a shortcut, cutting the distance down to 12 parsecs.
For no reason at all the two Swedish characters talk to each other in English.