I am an author. I published a children's book through a Canadian based self-publishing company and received my royalties as CAD currency. Do I report this as CAD or USD?

[hbl3973]

You should convert it to USD.  You can use a website, say

 https://www.x-rates.com/historical/?from=USD&amount=1

to look up the exchange rate for the date you were paid or the royalty check was issued.