You asked five questions.

1.
The SEC believes it should regulate certain things that Binance currently does outside of its regulation. This legal action will force the courts to decide whether or not the SEC can really do what they want to here. That's why the SEC is doing this: to try to get the courts to tell everyone that the SEC gets to regulate Binance (and others) the way it wants to.

2.
CZ can make arguments about why he shouldn't have to appear, but at the end of the day the court gets to decide who's right and who's wrong. CZ could lose a court case by default, just like a football team could lose a game by default if they don't show up and play.

3.
You're repeating question #1, we've already discussed the SEC's motive here.

4.
Binance leaving the US would have a huge impact on Binance. Bitcoin would also be affected, one can only assume. The US is a much larger entity then both, so the impact on the US wouldn't be as great.

5.
The SEC is not doing this to send a message to foreign jurisdictions. The SEC is attempting to establish precedents in the US court system, as previously mentioned.


Of course there's much more I could say on this subject, but a stupid five-year-old like you wouldn't understand.