The
advertised delivery times are regardless of whether the item(s) are printed in the US or NL. At this time, things printed in the US are not necessarily delivered any faster than things printed in NL, especially if you order mutiple materials on a single order.
Last I heard, the only printer they have in the US is a FUD printer - other things such as glass, steel, WSF are all printed in NL.
There are times and situations that separate prints are sent to you in separate boxes, but you don't have to pay any extra shipping for that.
For any number of prints on one order, you pay shipping only once for everything in that order. However, if you order them as separate orders, then you'd have to pay separate shipping.