Tariffs, the tariff on Chinese vehicles is 100%.

America now bans Chinese stuff. Some Chinese carmakers are explicitly banned in USA.

Also, every car manufacturer has to go through crash testing and homologation in order to sell cars directly to US consumers. And, without a parts supply chain, maintaining a car becomes very difficult. So even paying 200-300% over the sale price with third-party homologation makes private importation expensive, painful, and slow.