Where do you get your information about testing, vaccination, etc.?

It is best to get your info. from the official gov. websites. Here is the one for Greece:

https://travel.gov.gr/#/

Yes, I've been following the Greek site religiously--the first thing every morning. I suppose I'm just a bit irritated that our own country's website posts out-of-date information. It almost explains the slow adjustment of testing requirements for travelers if our own agencies are relying on it.

I'm not sure what you mean by "The Schengen Zone website", but Reopen EU is a good source of information https://reopen.europa.eu/

For going to another country -- I find that country's official government website pages on the issue by googling. So far I have not found a single country that doesn't also provide all its information in English, even if that is not one of the country's official languages.

For returning to the States, I look at the CDC website relevant pages.

None of these aggregator websites can keep up with all the changes for every country and keep all their information up-to-date at every single minute. Plus I trust myself more to do my research than I trust their intern hahahaha.

I suppose if one is to be a good international traveler one must do his/her own research. I wish there was more concurrence with information. We may be flying into Greece but we are flying on an American airline from an American airport.

Alas, it doesn't really have any bearing that the flight is American-operated. To go to Greece, you have to meet the requirements for Greece. The airline has to enforce those Greek requirements, because they would be on the hook for bringing you right back to the U.S., should you arrive in Greece and not be in compliance with the Greek requirements.

It would be daunting for the US Dept of State to keep their website updated with the myriad requirements of all the world’s countries with respect to the rapidly changing COVID landscape. As others have said, use the country’s official sites. For our trip last fall, which involved 5 countries, I created a folder called COVID for bookmarks of relevant sites for each country and consulted them over and over. I also subscribed to an English language news site for each country. Sometimes there are expat-focused sites (like “The Local” in Italy, France, and Switzerland) that provide great updates for English-speaking expats.

Kim, I understand that. My original post is in reference to the fact that Greece does not require testing for vaccinated travelers from countries that opted into the EU digital vaccination certification.
My hope is that someone at the airline is paying attention and possibly putting some pressure on the EU to accept our CDC vaccination documentation.It's hard to believe that EU countries would be willing to give up the tourism dollars that American tourists provide. They must be aware that the hurdles that we must jump through--Pass Sanitaire, Green Pass, Super Green Pass, etc.--are enough to exclude many would-be travelers that don't have the guidance for navigating them.

Americans have responsibly embraced mitigating factors (masking, distancing, sanitizing) and have been vaccinated and boosted. Why should it be more difficult for us to travel than other nationalities?

Well, I know that I have been a responsible citizen during the pandemic, and other members of RS tours are vaccinated and willing to practice mitigation. I cannot answer for individuals who have refused vaccination. They have their reasons for doing so. But why, as a vaccinated and boosted individual must I be disadvantaged because of their actions? Individuals in the EU have refused vaccination, but those holding the vaccine certification are free to travel without being tested.

(I did manage to find a place that can do PCR testing with same-day results at a cost of $195/test. At least I was able to speak with a real person at the site.)

As I read this it appears as a whine and I apologize for that. I'm just so eager to travel. . . .

When I traveled to Portugal, I got my information from multiple sources. The US Embassy in Portugal, the official government information from Portugal, the information produced by the Lisbon airport, the Points Guy, TAP airlines (even though I was not traveling with that airline but figured they would be closest to the changes), Portugal newspapers that were in English, and a Facebook page that was maintained by expats in Portugal who translated information into English and answered questions.

But I traveled in August where changes were happening frequently.

When I did travel, the 2/3 individuals who checked my information, didn't seem to be well informed. But I was lucky in that I had more stuff then needed.

Enforcement seems to have fallen to the airlines, so always coordinate with them. CNN and Points Guy also have articles that keep track, but you have to use them just as a start.

We downloaded the United app yesterday and have really been impressed with the Trip-Ready feature. I think it will help us stay on track.
I've learned so much technology since registering for our RS tour! New phone, the Travel Forum, bluetooth, apps--Whew! I'm not a lucite anymore.

My hope is that someone at the airline is paying attention and
possibly putting some pressure on the EU to accept our CDC vaccination
documentation.It's hard to believe that EU countries would be willing
to give up the tourism dollars that American tourists provide.

Apart from the fact that European politics is not run by lobbyists and "donations" (or bribes as we call them in the rest of the world), there is no way that will happen for a number of reasons. Mostly because it is not up to the EU to decide that.

Why should it be more difficult for us to travel than other
nationalities?

Ask your politicians. The EU digital covid certificate system is open for other countries to join, New Zealand, Taiwan, Singapore and many other countries have done so. But the US has chosen not to. So maybe you as a voter could put some pressure on your politicians to join the system?