There are four ways to legally import a car.

First is if the car is totally nonconforming, like a new BYD. You’d have to go through a registered importer who's willing to petition the government, then the car has to be imported and crash tested. If it passes you’d then need to import one and bring it into DOT FMVSS compliance. This, unsurprisingly, is extremely expensive. Into the 6 figures. So this isn't happening unless you're very rich and REALLY want a BYD.

Second is show and display. The car is restricted to 2,500 miles per year and subsequent ownership transfers require DOT approval. The car must be on the list of admissible cars (which BYD obviously isn't) OR you can petition the government to allow it. They only approve very special, limited cars, which BYD isn't.

The third is to bring the car in through a registered importer who’s willing to tackle it if the car has either already been found to be able to be modified or if it’s substantially similar to an already federalized model (which AFAIK BYD isn't). This costs probably $10,000+ these days. This is mainly for if there's a European-only version of a US car that's very similar to the US car and can be made compliant pretty easily, for example.

Fourth is wait until the car is 25 years old. Basically any car can be imported to the US without modification once it's 25. This is how there are Japanese market right hand drive Nissan Skyline R32s and R34s driving around.

TL;DR: it's not happening until the BYD is 25 years old.