Like pretty much every motorcycle made, Harley buys suspension, forks and shocks, from Showa, or in the case of their new 500 and 750 Street models, Endurance of India. Starters are either Nipponseike or Hitachi. Cast wheels come from Australia, wire wheels from Japan. Brake calipers can be either Kelsey-Hayes (US), Tokiko, Nissan (both Japanese), Endurance of India for the Street Models or Brembo of Italy for the touring bikes and V-Rod line. Brake rotors usually come from Sunstar of Japan. Coils and some other electronic components that were once sourced from Delphi in the US now come from three or four Chinese suppliers ( and my brand new Chinese coils failed the primary and secondary resistance tests right out of the box!). Pistons come from Mahle of Germany (best pistons you can buy honestly so no complaints), and V-Rod and Big Twin transmission gears and shafts come from Getrag of Germany. Harley has never built the whole bike in house. The suppliers have changed over the years, forks once were from Ceriani and shocks from Gabriel, brakes were sourced from Lockheed, etc.. Perfectly normal automotive and motorcycle industry practice. My BMWs are likewise assembled from components from multiple vendors, including some vendors Harley also uses like Mahle, Getrag, Showa and Nipponseike. I am pretty sure the powder forged conrods in my V-Rod are from the same vendor BMW and Porsche use. They have "Germany" stamped into them in big bold letters.
The only motorcycle company I can think of that even came close to making every component in house was Moto Guzzi. Even still, their starters were the same as those used on BMW twins and some air cooled VWs.