I don't know where the rumour started but I just read in a Newsarama review about JLI, that Booster himself may in fact be Canadian.
Here is the quote by reviewer Edward Kaye:
"We now have a UN-sanctioned team, with each team member hailing from a different county. The team is headed up by Booster Gold (who is rumored to be Canadian now), and is based out of the Hall of Justice."