I accept your foreign muscle car challenge. Merriam-Webster says it's "any of a group of American-made 2-door sports coupes with powerful engines designed for high-performance driving", but c'mon. It can be other countries.
So, we'll just go with the rest of the accepted classification. Muscle cars are usually V8, rear wheel drive, and usually (not always) made from an existing platform. The Dodge Viper is a muscle car, but it's a V10, and the chassis did not exist before Dodge made the Viper. I'll pick some from some different areas.
From the UK
Jensen Interceptor
Sunbeam Tiger
Triumph TR8
There's plenty of others.
Germany
Mercedes 280 AMG
BMW M5
Australia
Ford Falcon
Holden Monaro
South Africa
Ford Sierra XR8
Chevrolet Firenza V8
I'll do more when I have more time. (If anyone cares.)