While I've never experienced a similar situation myself, I've had several friends and acquaintances who have had similar issues with tech jobs that required relocation from Canada to the US - from having jobs rescinded last minute after selling their home in Canada, to being downsized due to company cutbacks within days or weeks of starting the new job (after all, new employees are more likely to be let go during those times).

In short, there is always a risk associated with relocation for work, and the job or location must be worth that risk in order to upheave your life and move for it.