General Question on European Travel

Short answer: It depends. For many countries it seems to be the where you have been in the last 14 days that is of importance. For some countries, transfers do not count as being "in" the country, for others they do.

I believe it has changed in the last few days, but for some time prior to that, an American tourist changing planes in London on the way to Italy had to quarantine upon arrival in Italy. That's an example of what can happen if you have a connection in Europe and get unlucky.

Whatever you do, don't buy any plane ticket where you have to connect from an airport in the U.K. to get to Europe. That has been problematic.
Getting a Covid test and results in Europe is very easy. It is a moneymaker. If you get up early enough you can get one for free outside most major train stations in Italy in a tent operated by the Red Cross.

It’s a complex situation that can change at short notice. You would be better transferring in the USA than in Europe or at least within the Schengen Zone.

Generally, countries look at where you have been in the past 14 days. It’s advisable at present, if you want to derisk your trip, then just visit one country.

You can get Covid tests widely throughout Europe. Some are free, but you have to pay for most. They are not necessarily a money making scheme, as they cost money to administer - why should foreign tourists get free testing? If you can afford a trip, you should be able to afford to pay for a test.

As others said, "it depends" and it changes frequently. It is dependent on the rules at the time of the country your are transferring in, and the rules of your destination country.

Generally, a transit is allowed in most cases by the "transit country" without imposing any testing or quarantine requirements, though at times, there have been countries discussing not allowing transfers. A transfer in this case means land, stay in the secure zone, and leave on another flight in a defined period of time, usually less than 24 hours. Leaving the airport is entering the country, and you need to meet all controls of that country, as well as your destination country. Basically, you are subject to controls for any country you stepped foot in for 14 day prior.

Your destination country may also impose controls based on countries you transited through, as the case with the UK and Italy illustrates.

A good resource is the IATA Travel Center, they have a handy map that lists entry requirements.

https://www.iatatravelcentre.com/

You can get Covid tests widely throughout Europe. Some are free, but you have to pay for most. They are not necessarily a money making scheme, as they cost money to administer - why should foreign tourists get free testing? If you can afford a trip, you should be able to afford to pay for a test.

Are these PCR tests? What's the turnaround time to get results? (I never had a test, not sure the current state of tests or new tests out there.)

Just to illustrate, here is a testing service at Berlin airport and here is another one with multiple locations in Berlin. I'm sure there are other options there. Both offer antigen and PCR tests with good turnaround times depending on the type of test. I haven't been to Europe since 2019 (sigh) but, from what I read on this board, getting tested over there is the least of the traveler's worries.

In France, you can get an antigen test (as a tourist) for €29. Easily available at almost any pharmacy, and results in 15 minutes.

I paid €112 for an antigen test as a tourist last week in Norway. In Norway, only a few private clinics offer tests for tourists, and their hours are limited, making it more complicated to get tested.