I think its actually the rule in GB too, if the junction is unmarked. However 99.9% of junctions are (usually clearly) marked so this generally avoids confusion.
not true. here is the rule for unmarked crossroads in Britian:
Unmarked crossroads are by definition crossroads that have no road markings or traffic signs on approach to indicate which road has the priority. The width of the roads that form the cross has no bearing and neither does the amount of parked traffic in the streets. If there is nothing to say which direction gets the priority then neither one does.
The safest way to use this type of junction is to assume that neither of the roads has priority. Simply pull up near the junction in an emerging fashion, prepared to give way to anything that is coming. Make sure that you look effectively in all directions before you move off again.
If you are involved in an accident at this type of junction then it is automatically half your fault, because if you had stopped and given way then the accident would not have happened. The same of course applies to the driver of the other vehicle.