You filed I-140 due to different reasons , such as your company sponsored you for H-1b visa, filed LC etc. If in the meantime your I-140 got denied or H-1B visa expired and you got Canardian PR and you are in Canada, you can apply for B-1 for US. But there has to be a reason for your visit to USA such as you are going back to wind up your stuff, meet old colleagues etc. Granting B-1 shall have no relation with your previously filing I-140. As long as they see your intention of coming back to Canada and your visit to US is just a temporary there won't be any problem for B-1 visa. BTW most Canadian PRs and citizens come to US over the weekends to buy cheap grocery anyway ( for example from Vancouver to Bellingham ).