If a vehicle was never sold in the US and is not FMVSS compliant (with a sticker), then the RI has to prove every piece of consequence IS compliant. Airbags tested to DOT standards. Headlights. Taillights. Seatbelts. Wipers. Crash safety. Dash lights, warning lights, backup camera FOV. TPMS. The list is like 10,000 things long.
Probably it does meet 99% of them , and the non-compliant things are an easy fix (we’re changing speedo in mine to mph).
The trick is you have to document and prove every single item on the list, often with lab testing. It takes years, and often millions of dollars.
Regular passenger vehicles have a lot of standards they need to meet, which usually means manufacturer participation. Has BYD gone through the process to get passenger vehicles approved for use in the US? Otherwise, sure, you can get it imported under a conditional use to bring it to car shows, but not for daily use.
> Nonresidents may import a vehicle duty-free for personal use up to (1) one year if the vehicle is imported in conjunction with the owner's arrival. Vehicles imported under this provision that do not conform to U.S. safety and emission standards must be exported within one year and may not be sold in the U.S. There is no exemption or extension of the export requirements.
While the vehicle can't be sold in the US, and must be reexported after a year, there's nothing on this page that says the nonresident can't lend it to a resident for most of the year. If money isn't really a problem, buy overseas, pay a nonresident to arrive in the vehicle, and after a year, export it and sell it and repeat. Nothing on this page suggests the vehicle couldn't leave and re-enter, but that seems like asking for way too much trouble, I wouldn't be surprised if someone at the border is keeping track of VINs. Since BYDs are sold in Mexico, you don't even need to deal with shipping, just drive through the border.
It's tricky with a car that has never been sold in the US, but with something where production for the US market ended, but other markets continue, you end up with things like a 1990s VW beetle with a 1970s title. shhh
[1] https://www.cbp.gov/trade/basic-import-export/importing-car
And you can buy a BYD in America. There's just a pre-Trump 100% tariff on Chinese EVs with bipartisan support that isn't going away any time soon.