Since the tartan in the B&W photo seems to have a bold light stripe, I'd guess it was a Gordon. And there was a 50th Gordon Highlander regiment based in Victoria BC during WWI, so they could have been participating in a parade in the US where the Pintail was sold, or maybe Pintail was sold in Victoria. Judging by the hat styles (straw boater, newsboy caps, etc.) the time would be about right. Only thing that keeps me from making the prediction is that the sporrans in the photo seem to be black hair with white hair tassels, and the only photos I can find of the 50th are just the opposite.

BTW: the Stars and Bars was the nickname of the Confederate national flag with only three large stripes, two red with a white in the center. The blue field has white stars in a circle, either 7 or 13. The well-known red flag with saltire and 13 stars was actually the battle flag, not the national flag.