Again, all of that is really testable. You can even blind test yourself at home.

Any salted meats will naturally form MSG when the glutamic acid binds to sodium. Pretty much all processed foods contain msg even if it was not an additive because it naturally forms on the foods themselves when free glutamate binds to salts. If you had any form of Japanese food cooked with kombu or seaweed, it also had high msg content.

None of this is even unique to Asian foods. Most cheeses are extremely high in msg, especially aged cheeses like Parmesan. Pretty much all savory foods contain some glutamate and glutamic acids.