"We’re the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States ... with all of those benefits. It’s ridiculous. And it has to end."
I actually listened to what Trump said on this, and I don't think it's fair to say that he's claiming we are the only country with birthright citizenship. The ellipses are misleading -- he said it all as one continuous statement. In other words, his comment about us being the "only country" included the context of the benefits we provide, and the other countries that do offer birthright citizenship don't package it along with those same level of benefits.
That's still a false statement because of Canada, but otherwise, the vast majority of other countries that do offer birthright citizenship are comparative shitholes where birthright citizenship doesn't include a ticket to a bunch of free social welfare benefits.