Not visas which are visitation permits. They are non-citizens who live in the United States. This is not visitation.
Revoking a green card is akin to expulsion from the country. And can only be used when laws are broken, treason is committed, or terrorism is waged.
In the case of the Columbia student, he was accused of terrorism without trial and had his revocation signed single handedly by the Secretary of State. This is a first time for the law to be used.
CBP/ICE has a pretty detailed explanation on their website that you can lose permanent resident status by remaining outside of the country for more than one year and failing to retain a bona fide residence and presence in the USA (US job with annual 1040 tax filings, residence, identity documents, etc).
I would wager that a scenario such as remaining overseas for multiple years is a much more common way for people to lose US PR status through negligence/lack of action than for people to get their PR status revoked through some legal process initiated for treason, terrorism, etc.
The courts said, “no.”
But the US State Department would still refuse to provide consular services.
The courts enthusiastically said “no”.
You also get other benefits too though. If you ever become desolate or need help getting home, embassies can help or provide a loan. If war breaks out or some natural disaster happens, America will come for you. You get the power of our passport. You can still collect benefits like social security.
Pros and cons.
Sort of. The state department will arrange evac, but if it's a charter on a PJ, you'll be on the hook for it and will have to sign a promissory note for it.
Sending in the military is very rare. You'll have better luck with a private security company, but they aren't cheap.