Here’s a few answers to your questions:

Q1. Led by representative Maxine Waters, the committee wrote a letter. Did I miss something? Does Mark Zuckerberg respond to mere letters from Congress?
A1. Yes. I believe all government and legal entities communicate by mail. That’s also he was last invited.

Q2. In a world disrupted by internet companies, who do you think wins? Elected officials or BigTech executives?
A2. Let’s hope it’s elected officials. After all, we do live in a democracy and and the only way we get to determine what’s “evil” and what’s not is through our elected reps. (see Net neutrality, monopolistic practices, tax payments, AML/KYC, etc.) The less we think it’s us, the more privacy, work protections, the environment, infrastructure, personal security, etc. get handed away.

Q3. In 2020, do we have any hope at all of technology companies doing the right thing?
A3. Yes, thank you EU. GDPR is a start and more is coming. Now they’re going after monopoly and taxes. In USA (particularly now with the swamp in charge), No.

Q4. Whatever opposition Libra has, do we expect the world will be able to resist it? Do we think they care about EU bankers or U.S. congress (women) really?
A4. Not sure what you mean by EU bankers, but see A3.