Do crypto exchanges must get authorization from US government before they offer any service, program, or features? Do you think US government or SEC has the role as the regulator in crypto space?
No. The SEC has the role as the
regulator of the "securities" space, more precisely: it regulates exchanges which offer trading of securities.
If a company is launching a security but calling it a "cryptocurrency", and it is traded in the US (on centralized platforms) then the SEC has the right to intervene.
ICOs in almost all cases are securities, they work very similar to an European financial instrument called "participation certificates" which could be described as a share which does not give you any kind of rights - when their issuers go bankrupt you typically lose everything if you can't sell them fast enough.
As far as I know, crypto is ideally a decentralized system, it is not regulated by any institution. If US government or SEC can regulate crypto exchanges, it means they also regulate crypto as a whole.
The first sentence is correct. But the second is not. As I wrote above, Bitcoin (and a very limited set of altcoins) have no character of securities, because they lack a centralized "issuer". So the SEC has no authority over them, nor over the way they're traded.
Anyway, I have no problem if SEC regulates Binance US. But I disagree if they are trying to intervene Binance global. Binance global is not subject to US jurisdiction, it is not located in US territory. Another thing is that what SEC accuses to Binance isn't proven yet. We can't judge SEC is on the right side while Binance is on the wrong side. Everything isn't clear enough, so I don't think we take a conclusion for now.
Here I'm partly agreeing with you. The legal process is still open. But I think the probability is high that Binance US will be fined or even closed.
Suppose we say you're right and SEC is really just pushing for the reform in the Altcoin world (I don't even think it's reform to me this is literally just purge all altcoins), what's going to happen to the rest of the "not shitcoins" spectrum of the altcoin industry? Are they going to be regulated?
The SEC cannot "regulate altcoins" if they weren't issued in the US and aren't targeted to US customers. They can only regulate companies offering services with them and create their revenue/income from these services, e.g. offering trading, "staking" etc.. That's a big difference.
They can also not regulate altcoins which are not securities. But ~98% of them have the character of a security because they've a centralized issuer. One of the few coins which aren't a security is Monero, there are also smaller coins like Groestlcoin and Namecoin which are decentralized enough. Litecoin is already an edge case (due to its instamine accusation) but I think probability is high that the SEC wouldn't consider it a security, in Europe I'd be confident it would not be regulated by the upcoming MiCa crypto regulation.
Plus even if they did only intend to attack shitcoins and not bitcoins, their attempts had left bitcoin in a pretty precarious state price-wise.
That's because many traders panicked and sold, and whales made money shorting the coins because traders are dumbly dumping their precious BTC
If hodlers would understand what this SEC thingy is really about, then they wouldn't have reacted this way, and the price perhaps would be still at 27K (by the way, we're over 26K again).
(BTW: for better understanding of the OP I added a sentence which hopefully helps to clarify what I meant, in bold.)