Reneging a postdoctoral offer from Canada due to Canadian work permit delays I was recently working as a postdoctoral researcher in the United States. My supervisor was in close collaboration with another professor in Canada and therefore I expressed interest in joining the team in Canada with which both professors responded positively. 

I should mention here that I am a foreigner to both countries. Therefore, I had to apply for a work permit to move to Canada from the US. In addition, I require a full-job to remain in valid status in the US. 

I applied for a Canadian work permit based on the job offer as early as I could---which was only three weeks before the tentative start date on the official letter. The processing times estimate on the Canadian website for such a process were two weeks at the time. Happily, I resigned from my US job to finalize my move and get ready for the visa. 

Unfortunately, the visa has not yet arrived for another 4 weeks and my US status will expire soon unless I'm hired immediately. Therefore, I applied for a local postdoc position and received another offer. My previous supervisor in the US would not be able to re-hire me immediately and the current offer is the best option so far. 

My question is as follows: I understand the resigning was a mistake in the first place. However, Is it justifiable, professionally and ethically, to accept another position in the US?  The position in Canada is ideal to me, but unfortunately, I have to commit to the US position for about a year if I sign.
Whether this specific Canadian professor would understand we, of course, cannot tell. Yet people tend to be understanding of delays due to bureaucratic visa issues, or things just not working out - especially if you communicate this clearly. I would suggest reaching out to that professor, laying out the situation and seeing if anything can be done. Perhaps they're willing to delay your start by a year, perhaps not. What you don't want to happen is the professor reaching out to you a month from now, asking when you're planning to show up, and you having to respond that actually you started a completely different position.

A sidenote is that you'd probably not be legally bound to a one-year commitment in the US, but I think you're right in not wanting to burn those bridges before they're even built.