What I don't understand is how this squares with the Speech or Debate clause. Aren't members of Congress protected by the same sort of legislative immunity as they have in the UK, Canada, and Australia (where they call it "parliamentary privilege")?

Somewhat. Article I, section 6 of the United States Constitution: "They shall in all cases, except treason, felony and breach of the peace, be privileged from arrest during their attendance at the session of their respective Houses, and in going to and return from the same; and for any speech or debate in either House, they shall not be questioned in any other place."

How that plays out in this situation, I'm not sure, since I'm not a Constitutional Scholar, nor a lawyer.

They would simply charge them with a felony--revealing classified information.

INAL but I believe they could be charged under the Espionage Act (18 USC sec. 793) for leaking national security secrets, which is a felony, and they would lose privilege.

That seems to be no different than the law applied to any citizen.

I think it's more a case of, "oh, I see you don't want to be re-elected. We can arrange that" rather than direct prosecution.

That's why you don't see guys like Bernie Sanders on those committees :-)

The security clearance process basically looks for reasonable, honest Americans free of foreign influence.

If government actors are abusing their power to such an extent that reasonable, honest Americans free of foreign influence feel morally obligated to blow the whistle, then there are going to be more leaks.

It's not a flaw in the system; It's a safeguard against corruption and abuse of the system.

That's not what is being discussed here. What is being discussed is the leaker doesn't appear to be a standout individual. He isn't the top of his field. He doesn't have numerous advanced degrees. So on and so forth. He is "garden variety". So, given that, if a "garden variety employee" can get access to all this data, just how many ordinary Joes have access to it? The more people, particularly those low on the totem pole, the more opportunity for leaks to the wrong people.

* The security clearance process basically looks for reasonable, honest Americans free of foreign influence.*

That might be enough for domestic intelligence, but it's really shooting yourself in the foot if you apply "free of foreign influence" to overseas intelligence operatives. (Because you'll never be able to recruit anyone whose exposure to the target culture is significantly deeper than a semester attending a foreign university ...)

Everyone here seems to be assuming that tech company leaders actually knew the whole picture, but that isn't necessarily the case.

Think about it: Let's say you're the CEO of any of these companies. If someone from the NSA or the FBI serves a top secret FISA order on some poor SRE in your datacenter, do you even qualify as one of "those persons to whom disclosure is necessary to comply with such Order", or an attorney?

Now, maybe your General Counsel knows what's going on, or maybe the knowledge is scattered throughout your legal team. Your lawyers, who are supposed to be representing your interests, are now bound to keep these secrets from you, and possibly even from each other. This is something that affects millions of people, and you can't do anything to fight it, because you aren't necessarily allowed to know what's going on in your own company. The only sign might be that a few previously-happy key employees suddenly seem stressed and quit for no apparent reason.

Freedom of speech is such a basic assumption in our society that we struggle to understand the full implications of what can happen when it's taken away.