A national currency is already centralised. My trust towards these government centralised crypto(s) comes from the government who issued them, the same trust I give to their fiat counterpart.
Partly correct. Digital tokens of existing centralised money systems are acceptable to me because we have been using them for years (bank accounts, credit cards, phonecards, supermarket points...)
A centralised crypto based on a centralised national currency offers no difference in central control. If I am already using that fiat for years, I have no problem with that centralised national crypto. When I put my savings into a bank, I have to trust that bank. The bank then issues this centralised bank crypto, the trust I have with the bank is transferred to that crypto. Same with credit cards.
Bitcoin is different. It has no trust to inherit from. That's why decentralisation is so important for bitcoin. Decentralised hash power and blockchain invokes trust in a trustless environment.
Where is the not correct part of my sentence?
Let me explain better. I wanted to tell exactly that you tell in the first part but in the second I had another aim and another meaning. If behind the digital coin could be an unknown group of peoples (or only one rich person) for you and create this coin (closed or open source this is not the problem in this case) you will believe this coin? I think not because behind this coin is something that has not your trust: you don't know who are they. This case is the case when we have e centralized digital coin (group of people who own this coin, or even one rich person) and you normally cannot trust this digital coin. So who is behind the digital coin is very important for you (and for everyone I think). This is the case bolded by you in my phrase and its meaning (what i wanted to tell with it).
It's ok now?
Bitcoin is another case which have nothing to do with the entire phrase. Bitcoin is decentralized. In my phrase is told only for the various centralized cases.