Possible Clues:

• The automotive industry
• Tried to (anag.)
• City in south-east Michigan on a river of the same name
• Largest city on the border between the U.S. and Canada
• US “Motown” city
• Largely superfluous note about Motown
• Detective encountering nonsense about one US city
• "Motor City"
• City right for some foreigners outside – and for their sort occupying it
• Tried to, working in a US city