After specifying the city where the publisher is located in, would I need to include the country? I faintly remember my instructor mentioning that if we only said London he wouldn't know if it's London, UK or London, Canada. This is what my citation looks like
Swope, Kenneth M. The Military Collapse of China’s Ming Dynasty China, 1618-44 (Asian States and Empires), 1st ed. Abingdon, Routledge, 2014.
Do I have to specify any country or is this acceptable? Thank you so much
In Chicago format, at least, you don't have to list further information if it's a major-major city--London is a great example of this, actually; I wonder what format your prof is talking about? You'd have to say "London, Ont." for the Canadian one; "London" would be UK.
When I Googled for examples of your specific case, I got both:
The major publisher/database site Taylor & Francis requires Chicago format citation, and one of their examples of proper formatting (PDF) is from Routledge. They use:
So I think whichever way you go, you have solid backup to support yourself if the prof questions it.