⁸I don’t know what data they have at hand to work with, the following is mainly guesswork / how I would do it:

As far as I know, US authorities have quite liberal access to data stored by US companies (due to the cloud act even if the data isn’t originally stored in the US), especially in case the data is about non-citizens where some of their protection laws don’t hold. Most social media accounts are tied to phone numbers and/or email addresses.

If I was in their place, I’d have a relatively small database with all (or at least all non-US) phone numbers used for social media accounts, with the email addresses tied to those accounts. If a visa-applicant applies and I get their phone number (email address),

1. I’d query a list of all accounts for that number (email) to get the associated emails (numbers).
2. With those new emails (numbers) I’d repeat step 1

If you call the office or enter your number in your application, they might get some accounts. If you associated an email address to that account, they might get additional different accounts by that email. If those different accounts have a different phone number associated to them, they use that new phone number to get more accounts. rinse, repeat.

[Edit: This process would be completely automated, of course. Not manual.]

The consequence of being caught lying might be to get your visa revoked / denied once you are already in the US at the airport, which would be highly inconvenient. Or, if they get suspicious, find something else, and get annoyed, maybe it could even be punished? I don’t know.

You could maintain a separate phone with a separate phone number and separate email addresses for accounts you want to keep secret. Or maybe get a fresh phone number / email address just for the trip. But that’s quite a bit of effort to maintain consistently.

1. It’s not a visa but an ESTA. The visa is still granted on the fly on entry.
2. The U.S. require the same the other way around, only the one granted by the EU is $10 cheaper and valid for 3 years instead of 2, so still U.S. citizens get an advantage
3. EU citizens (like all other non-immigrants) have to, as far as I understand, disclose all their social media accounts when applying for a US visa

Sources for (3):

For VISA applications, https://travel.state.gov/content/dam/visas/Enhanced Vetting/CA - FAQs on Social Media Collection - 6-4-2019 (v.2).pdf should apply.

What if applicants participate in multiple online platforms? Are they being asked to list all of their handles, or only one?

Applicants must provide all identifiers used for all listed platforms.

I reached that document via https://www.ustraveldocs.com/de/de-gen-faq.asp#qlistgen21 (“Apply for a U.S. Visa in Germany”) and didn’t find any hint for exemptions for German citizens or E U citizens, so I assume it applies. (But I might still be wrong.)

Since it’s not Twitter anymore, we should replace “tweeting” by “Xcreting”. (It’s not mine, saw it on Reddit, but I think the idea deserves more exposure!)

I live on 7 acres of mostly heavily wooded land

Well, the activists target SUVs in the middle of Hamburg. That’s not really a comparable situation. I agree it would suck if you visit a big city and get targeted there, but I would hope the activists can decide between a polished up city-only SUV and an actual working-vehicle and act accordingly.

Well, if they want to go shopping right now, chances are for this one trip they’ll take their spouses smaller car, public transport or maybe even walk. If SUVs become generally unreliable (because you never know if you have air in your tires when you need it), people will look for something more reliable. They’ll bitch about it, they won’t act out of conviction or so, but who cares.

They target SUVs and alike. In what area do you live that a much more affordable and less gasoline consuming car wouldn’t work for you?

That is why I like this targeted actions over the gluing themselves to the road ones. This is targeted to people destroying the climate. I don’t think there is any good reason to drive an SUV or a sports-car in a city, and it is actively harmful. To pick up your equivalence: Feminists fight misogyny and inconvenience those guys actively showing it without necessarily alienating average guys.

Only “they” is actually “us”. We voted those clowns into office. We knew (or should have known, the information was available) better at least since the 1970s.

Controversial opinion of an atheist:

Most religion is incitement to hate-crimes. While I think Sweden has probably bigger Christian societies and should probably rather burn bibles, the guy burning the Quran is an Iraqi, and therefore choosing the Quran is understandable. Afaik, he protested against his own former repression by Muslim religion whe still lived in Iraq.

Religion is notoriously used to reduce other people’s freedom. Be it fundamental Christians e.g. in the US or Poland denying healthcare to pregnant women, be it the atrocities committed by the “moral police” in Iran, be it other religions killing people for their sexuality. I support the idea that religious law should be limited to followers of that religion, and no person should be forced in any way to follow or keeps following any religion. Those are fundamental human rights principles in my eyes.

Most religions try to impede the rights even of nonmembers of that religion. That is disrespectful as well. Burn any book or other goods you want, if you want to protest any of my convictions. TuX-puppets, books about string theory, the FSM, my national flag, I don’t give a shit as long as you own those things and you don’t physically harm others.

We’re going to be the first species to go extinct due to stupidity.

Because we act global. The mechanism isn’t new at all, though. We as a species are just as stupid as yeast: Watch a slice of bread mould. It starts with a tiny dot, within a day or two the whole slice is green and the bread already unrecognisable, after a couple of days the yeast will die because there isn’t any bread any more.

If we went back to that, I’d probably immediately miss the days when objects in our day-to-day were attainable for one Euro or so :-)