It's easy to hire Canadians even non-remote positions. The TN visa requires only a job offer letter and detailed job description for software developers.
There's no requirements for the TN visa holder reside in the same location as the business, to my knowledge. So a Canadian could reside in Washington and be employed in California.
I am a Cdn on a TN. There is very much an expectation that you will reside in the same location of the office. Its not as hard+fast rule (like the h1b1) but considering a random border guard could have a bad day and deny your TN based on whatever they feel like, I would strong caution against anyone living far away from their assigned office.
Also, if you're living in another state getting a US drivers license might be impossible (how do you prove residency if your work visa is for a different state?) . Some states don't require residency for a drivers license, (Oregon and CA don't) but you can get a RealID on your DL if you can prove residency. RealIDs are strongly suggested because you can use them to fly in the States, instead of your Cndpassport + work visa. Again, TSA agents have the legal ability to detain anyone on a work visa, so having a RealID lowers the chance of complications.
This is true, with TNs there is always have an element of chance. I've heard too many stories of people getting royally screwed crossing the border on a TN when it should have been no prob. If you are not working on US soil, the W-8BEN requires no one to "approve" you. It's just a form for them to justify not deducting tax.
There's no requirements for the TN visa holder reside in the same location as the business, to my knowledge. So a Canadian could reside in Washington and be employed in California.