Surely, that's not true. In America, the Niña, the Pinta, the Santa Maria, the Mayflower, and the Titanic are all far more famous than the Cutty Sark. I don't know why the Cutty Sark would be quite so famous anywhere outside the UK (and perhaps, given her history, Australia).
But it does raise the question: What is the world's most famous ship?
(Not fleet. Not sailor. Not navigator. Ship. And what is the most famous ship in Russia? India? China? etc.)