First of all, this board is completely irrelevant for the topic you have created. You should have created this topic in
Altcoin Discussion. From your conversation with their customer support, i assume that there was a misunderstanding. Of course if you import Ethereum private key in TrustWallet, you won't find your USDC on the Tron network.
Beside that, i'm also confused about what they say, isn't Blockchain.com a custodial platform? that means you can't get a private key to directly access your assets, right? if what i said is true, the only way to get your USDC back is to ask them to manually send the USDC to your wallet address.
Additional information for you, if you want to deposit USDC on the Tron network, so far only a few platforms support it, such as Bibox, Bitmart, CoinEx, Cointiger, Gate.io, Kucoin, LBank, MEXC, WhiteBit, ZB and Huobi.