The crocodylians once lived all over the world. Why up to 5 million years ago, the crocodylians had been living in Europe and other northern territories. In the early tertiary there were crocodylians living in the Canadian arctic. Their distribution over the globe was phenomenal. The only place that crocodylian fossils haven't been found yet is Antarctica. Judging by it's size and harsh climate, it's easy to understand the lack of a large amount of fossils being discovered there.
Still there's no reason why these animals wouldn't be found in deposits as recent as the Eocene, if not sooner.
For now though the crocodylians can mostly be found in all the worlds tropics. The only exception to this would be the alligatorines which can stand colder temperatures and thus live in the more temperate climates of North America and northern China. Even though they have a more restricted distribution and their diversity is nowhere near the amount that it was in the past, the crocodylians are still highly successful animals able to take full advantage of their environments. All but a few species are the top predators of their respective areas.