If you want to change the system intoto use metric units, you have to select a region (locale), which uses only metric units. Apple areis not very good when it comes to the worldinternationalization. Especially the many small nationalities suffer from this attitude. FeelIt feels like americanAmerican culture is walking all over you,,.
Go to System Preferences / Language & Region / Select a region which definitely uses the metric system. Maps should finally work.