Yes, we should consider state attack as Bitcoin threat model. But Bitcoin isn't useless or die if government actually put backdoor on some chip used by hardware wallet.
I'm not sure. I think if a significant number of HW are/were affected it undermines the whole ethos of Bitcoin.
So it's similar with "collect it all" approach?
Maybe; it's difficult to say. I think that governments around the world would prefer that we all use CBDCs.
I can give a reasonably plausible scenario: Perhaps the Bitcoin economy will be allowed to grow — with HW using compromised chips being standardised for KM — while the dollar/Euro/Yen/RMB economy declines. Then at some point in the future the United Nations announces that all BTC transactions are outlawed for [insert superficial reason here] and all BTC will be converted at parity with CBCD. Any address associated with affected HW/keys (majority) then has its BTC automatically drained into a new CBDC account. The minority not affected are offered amnesty. Such a "big bang" event would be difficult to oppose or counter given the massive additional power and leverage CBDCs would give any government over individuals. You may say this is a bit far-fetched - but it's plausible.
In terms of safeguarding/solutions:
1. Can we say that using non-specific generalized chips to store keys is safer as it's more decentralized and harder to backdoor than specialized secure elements? I believe Trezor takes this line.
2. Generating keys of device by dice/coins throws and calculating checksum word using offline air gapped devices that never connect to any network ever?
3. Using air gapped wallets for signing?
4. Developing subliminal free signatures so that it can be proven that keys are not leaked?
5. DIY HW projects using generalized off-the-shelf components?