Is there a difference in ingredients Mountain Dew from Canada to the US?

Yes

Here are some differences in ingredients between Mountain Dew from Canada and the US:

Caffeine: Mountain Dew in Canada contains approximately 43 milligrams of caffeine per 355-milliliter can, while Mountain Dew in the US contains approximately 55 milligrams of caffeine per 355-milliliter can.

High Fructose Corn Syrup (HFCS): Mountain Dew in Canada contains sucrose as its main sweetener, while Mountain Dew in the US contains HFCS.

Artificial Sweeteners: Mountain Dew in Canada contains aspartame and acesulfame potassium, while Mountain Dew in the US also contains sucralose.

Food Colorings: Mountain Dew in Canada uses Yellow 5 and Blue 1 as food colorings, while Mountain Dew in the US uses Yellow 5, Yellow 6, Blue 1, and Red 40.