Sometimes a writer will use "international" slang to make a character seem more salty and "regional" (frequently American versus British usage of a word). Sometimes, however, an expression is still considered vulgar elsewhere. When words like "bollocks" or "wanker" appear in a work whose language is otherwise PG, it creates dissonance for those who are familiar with them. (Though it varies according to region, age, and circumstances, "bloody" is about as strong a curse as "damn", and "bloody hell" is about the same as "goddamn". It refers to "God's blood" as an oath. Maybe.)