This is certainly not a given. However, absent a significant market leading aspect it comes down to value for money. FSD isn't yet a strong discriminatory quality, as much as a revenue model for something which is still contentious.

Tesla had a strong market leading aspect. It was range. BYD have access to world class battery innovations which are of course, uncertain but the hope of solid state batteries with 1000km+ range and fast recharge is on the table.

Tesla committed to the all glass dashboard. BYD was more circumspect and can more easily walk back to a mechanical switch dash, respecting emerging world views on safety.

Brand loyalty is a thing. A lot of tesla owners are brand loyal but new potential owners have aspects of brand identity in Musk they can (and do) use to rationalise their choice for alternatives. There is also brand dislike. Perhaps American consumers have forgotten it, but some people wouldn't by Ford because of Henry Ford snr.

So I come back to: it's not a given. The future is uncertain. This might be the end of Tesla market dominance in the US but it isn't written. The brands owner has a huge pile of cash. He can afford to weather storms which would break other companies.