True - sorry my mistake, I explained too quickly!
What I meant to say is that : the 2 years conditional PR rule is different than the "residency rule".
So if you have a conditional PR, you can be with your spouse anywhere ( or so it seems) and after 2 years together you will qualify for "full PR". that's based on the fact that you obtained your PR through spousal and CIC wants to see that the couple lasted at least 2 years.
Separate from that, there is the "2 out of 5 years" rule for ANY PR - conditional or full - needed in Canada to maintain the PR.... and in that case, either your follow your canadian spouse ( then it counts), but if it's a PR as you say the person itself needs to be sent out by a Canadian company etc ( in that case - it's not his choice to be out of Canada and put in jeopardy his PR, so it makes sense that the days outside of Canada count as well).
In the original question, it's the Canadian who would follow the future (american) PR in the US... so as long as they are together as a couple, the american citizen/PR of Canada will not loose his PR at 2 conditions: staying at least 2 years with his wife AND being 2 out of 5 years in Canada - both conditions apply, but in that case as she is Canadian, then it would help to fulfill both conditions at the same time...now - living with your spouse in his own country as a Canadian - not sure it would count as "accompanying the canadian spouse outside of Canada" - it seems a bit of a stretch ( although nothing in the CIC rule forbids it, but I think it would be subject to interpretation...).
Sweden