Uhm, the reason that more BScN may (or may not) be working in the US is probably due to the nurse's age. The BScN only became mandatory in the last year in my province. I believe there is one province still graduating diploma RNs. So if you went to nursing school
in most provinces up until the last five years you had a choice degree or diploma.
Most diploma nurses were married and had families and ties to the provinces that helped fund their educations and so would stay. The BScN holders tend to be younger without significant ties to their communities (other than parents and school loans).
The degree holders are more significantly in debt via student loans than diplomas nurses and of course went south if offered a full time position.
I work with several nurses (both degree and diploma) who have worked in the US. One broke the contract to return home, the others did the contract and returned home.
It's like Shay said, you can make statistics do whatever you want.