Your speculation of USDD's risk if TRX tumbles drastically is a fair worry. It’s curious that TRON endures, even when eclipsed by superior smart contract blockchains. TRON's journey forward is a riddle, and its manoeuvre through these tumultuous crypto waves promises to be intriguing.
TRON is available on a wide variety of exchanges. I guess that's an advantage it has among its more popular counterparts (except ETH). It's fast and cheap to use for day-to-day payments. Sometimes transactions are FREE if you have enough TRON Power accumulated in your wallet. If developers start building quality dApps on TRON, it would've surpassed Solana and BNB already. But everyone's focused on the big players because of the hype.
As a matter of fact, competing chains are much more innovative than TRON itself. Fortunately, not all hope is lost. The TRON blockchain is open source, so it's easy enough to improve or build a new project (fork) out of it. As long as decentralization is put first, there should be nothing to worry about. Just my opinion