Tesla's are essentially a luxury car. There's a limited market for luxury vehicles with several well established competitors. I think most people interested in buying a Tesla has already bought one and they're running out of potential buyers.

Because all the cars sent to China, Europe, the UK, and Australia are not available to be sold in the US. Last year they were only sold in the US so the US got all the cars.

The end of tax credits probably?

Seeing more and more is small scale sample size and bias.