It (the NSX) was sold in Japan under the name Honda NSX. It doesn't become an "American car" because they sold it as the Acura NSX in the USA.
Long story short, Honda wanted to sell more upscale vehicles in the US but figured Americans wouldn't accept an "expensive" Honda so they called the brand Acura. The original Legend and Integra were just as Japanese as a Civic or Accord just as the NSX is Japanese.
Whoever sibmitted this car and put "Home Country - USA" probably figured that Acura is a division of American Honda so "...it must be an American car..." but that person didn't realize that American Honda is a division of Honda and Honda is a Japanese company.
It's more confusing with Jaguar (Indian company?...formally owned by Ford?) but Acura is pretty simple.