I don't know much about it, but refusing the ships in the harbor could be due to crazy laws/restrictions the US has about them. For example, watercraft are not

I don't know much about it, but refusing the ships in the harbor could be due to crazy laws/restrictions the US has about them. For example, watercraft are not allowed within a certain radius of aircraft carriers, and if they get too close they can be shot without penalty. I don't remember the measurement, but it was large. Could really mess up the flow of a working harbor.