Is it possible to do a post-doc fellowship and/or get licensed abroad with a PhD in clinical psych?

[beherenow]

I just came back to the US after living in the UK for a year, and I'm already itching to get out of the country again. I've been accepted to a couple PhD clinical psych programs here and am deciding what do this fall, but was just wondering how difficult it is to work abroad once you are a licensed clinical psychologist in the US. I feel like I've heard that this is impossible (unethical, even) in a lot of places, but is this true/ are there any countries that will be more feasible (Canada I'm looking at you!)?

Thanks!