I thought you were talking about the refundabiluty of deposits, that is a difference in law.
Someone here recently did a calculation that showed US passengers are paying more total even with rhe extras. I haven't done the calculations myself though. I will also note that unless a US passenger boards in NY it is not cheap to get to a ship leaving from Southampton, which precludes using what appear to be nice but short notice fares for voyages leaving from that port!