Can I apply for a post-doc in global studies in North America? I am doing my doctorate in global studies in Germany, and would like to apply for a post-doc position in North America, especially in Canada. The topic I work on has considerable policy relevance, and I see that some North American professors are working in those areas. I am a non-EU citizen. Is there any chance that I will be accepted?
I can only speak for the US.

Yes!  US universities routinely hire postdocs from all over the world.  A few positions may be reserved for US citizens, due to funding requirements, but those will be indicated in the postings.

As one way to check, go to the web site of a department that interests you, find the web pages of some of the postdocs, and read their CVs.