Neither China nor the USA want an independent investigation. So it won't happen.
If there was such an inquiry and it emerged, without doubts, that the cause of Covid was reckless funding of dangerous research by the US in a foreign country, and reckless management of dangerous pathogens research by China, what could the geopolitical consequences be? Especially considering the control both countries exerts on media?
Amazing how if you scare people constantly, it can take over 2 years to start asking the right questions.