Here, we're discussing product as shipped, not product intercepted and modified. We're discussing if products are shipped secure or not.
The Snowden disclosures are important, but not relevant in this case.
Having state actors redirecting products after shipping, without telling the company or the client it's happening, and installing backdoors, has nothing at all to do with backdoors from manufacturers.
>a foreign nation state would pressure a manufacturer in their jurisdiction to include a backdoor
That absolutely is about jurisdiction and is a much bigger, more scalable attack than intercepting and installing implants. More to the point, it can be done at _any time_ not just the initial ship.
> If US manufacturers (or manufacturers in allied countries) do this, legal avenues exist to hold those manufacturers accountable.
With that context added, my point is that the US judicial system would never litigate against e.g. Cisco if they were involved. The issue is not the relation between the state and Cisco, it's the relation between the US justice system and the US national security apparatus that prevents any such litigation to happen.