Possibly the type of snow in the places you mention is dry unlike the UK where it is normally wet. In dry snow it can often be compacted and therefore the runway can be used safely with the compacted snow surface. Also dry snow is lightweight and can be easily cleared. With wet snow it becomes slushy very quickly and therefore is not acceptable for safe operations. Also wet snow has to be cleared before it freezes otherwise the runway suface ends up being like an an ice rink.
When busy runways are closed in the UK for snow clearance in the above situations, particularly for lengthy periods, it will cause significant disruption to schedules at airports like Heathrow, Gatwick, Manchester and Stansted where runway utilisation is high.
UK airports nomally plan to clear runways of all snow/slush contamination for the reasons given above.