There are plenty of pre-orders being sold in the US just from people who know of it. One of my fellow staff members online (won't say where though

) has looked up data fro mthe different stores for the company he works at. There are reserves upwards of 100 units at some single locations. There is enough buzz going around right that they don't need to advertise much.
Besides, here in the US, we have less patience for a product than JPN does. So if you start advertising tooo soon, people can lose interest. It you time it just right, which seems to be what they are doing, it will have the most impact.