Between years of layoffs and slow hiring, the power is completely with employers now.
Always was. Any illusion of workers having any actual bargaining power in the employee-employer relationship is just that — an illusion. When you have a multi-billion-dollar company with 1.5 million employees, do you think they actually ever cared about losing a few? This fundamental imbalance is why most countries have strong laws to protect employees from abusive employers. Give it a little time, and Washington will pass laws in response to this, and Amazon will begin to regret their short-sightedness, having made all future layoffs harder by being too greedy during this one.
That said, in this case, the employees still have a choice not to cede even more power to the employer unnecessarily. Amazon cannot force anyone to come back to the office. This isn't a totalitarian regime where secret police can drag you out of your bed at night at the behest of a company. You have a choice whether to return or not, and if you do not, they have a choice about whether to fire you or not. It's as simple as that.
If a large enough number of people refuse their false choice (resign or move back), they might relent. And if they don't, then you're still no worse off for having made that choice. After all, resigning with no severance provides you with absolutely no benefit other than a mostly theoretical opportunity to go back to Amazon in the future. Realistically, there's no reason to believe that they'll ever hire you without you moving back, so if you're not willing to move back, then there's exactly zero reason not to just let them fire you for refusing the forced location transfer.
Furthermore, if you were hired remotely originally, then you have a strong wrongful termination claim, because forcing you into the office is at least arguably constructive dismissal. (Yes, I realize Canadian law doesn't provide precedent for Washington State, but similar principles exist here in the U.S.)
And either way, if they fire you, you will likely be eligible for unemployment, which is free money. Amazon has to pay into that fund, and if they fire a large enough number of people, their unemployment insurance costs will skyrocket, so you'll be actively punishing Amazon by refusing to leave voluntarily.
So unless you're seriously thinking about moving back and working there in person, either immediately or in the future, there is absolutely no rational reason why anyone in their right minds would resign. Let them fire you, then file for unemployment and trash them on Glassdoor. That approach does the most damage to Amazon, both financially and reputationally, and it also maximizes your income. It's a win-win. Even better, when you tell your next employer why you left your previous company, you'll immediately know whether they are decent human beings. If they reject you because of it, you'll know that you don't want to work for them.