Pricing

Why is it cheaper to book a cruise through an American TA than a UK one ?

Because it is.

The cruise lines like their pound of flesh when selling abroad, and think they'll get away with it. Which generally they do, especially when many cruise lines won't accept bookings via a US agency unless you have a North America address.

But bear in mind the add-ons via a US agency - taxes & port fees are always included in UK headline prices.

Exchange rates make a difference - the pound is currently strong, so the gap has widened a little.

And pay a US T/A by credit card, not any other way, because they don't have the protection of ABTA.

But a late-booked deal in the UK will provide much bigger savings if you're prepared to be flexible about which cruises are available

JB :)