As I said you're making my research seem like more of a big deal then it is.
When my characters got to other countries, they will meet up with other gangs - they will help the gangs fight some criminals in that country - evil gangs or some other baddies. I will have AT LEAST one story in which they do that, then they beat the villains and the gangs the heroes worked with meet will become their allies and become honorary members or foreign members of their gang/group.
That is basically it.
I am using foreign slang to name foreign characters with.