The US licence also allows you to night fly if you have the required hours of training and currency. The piggyback one only allows you the same as your existing PPL. So getting a standalone US PPL will allow you to night fly in an N reg. I don't know whether local regulations in Belgium over rule this but it might be worth checking.
So when you go to the US make sure you do some of your hours training at night and then you will have this on your US licence. From memory its only 2-3 hrs training, but do check as I may be out of date.