Not if Amazon thought swift action would act as a deterrent in other locations. This specific thing has happened with other companies, so I don't think it's unlikely at all.
> Regardless, it's a decent argument for a nationwide union to avoid race to the bottom effects.
OK, but the question is whether these specific workers could possibly have any reason to vote against unionization. Maybe they don't find it plausible that a nationwide union will form, or maybe they don't want to deal with the interim turmoil that will befall them personally, even if they would support a nationwide effort. All seem like perfectly fine reasons to me.
It's not a 'logical fallacy' to not want to risk disruption of your livelihood, and that's the only relevant question to this thread: is there any set of facts that would reasonably lead the workers to vote against unionization? I think clearly there is, and there's no point arguing over subjective prioritizations. The workers are not 'irrational' for prioritizing their own jobs over the 'national action' that you seem to want. They may even consider that harmful. Not all workers have the same political opinions.
Regardless, it's a decent argument for a nationwide union to avoid race to the bottom effects.