Would the Yanks fight the Brits? Would the Canucks duke it out with the Aussies? How often would this happen?
The Australian and Canadian forces of the Western Front of the First World War did have quite a few problems while on leave: They were better paid than their British counterparts and rarely had any family to visit when they were given R&R. Free time, extra money, hanging out with your friends instead of dispersing, and stranger in a strange land syndrome among young men who viewed themselves as elite soldiers led to a number of incidents that eventually necessitated an official policy where Canadians and Aussies were kept separate both geographically and through scheduling while away from the Front.
Tim Cook's The Sharp End and Shock Troops mentions the Canadian-Australian rivalry a number of times, as well as the typical Canadian (although much less so Australian) leave experience.