ETIAS and EES

Neither is operational at this time. “Mid-2025” is the target for ETIAS, but, much like REAL ID in the US, it has been pushed back several times.

All you need is your passport.

If you don't have Global Entry for your return to the US, take a look at Mobile Passport Control. It might help to expedited your return.

https://www.cbp.gov/travel/us-citizens/mobile-passport-control

The EES is apparently going to start coming on stream in October this year. There has been quite a bit on the UK news this week about it's effect on Eurostar (which will need yet more rigmarole to board, including being fingerprinted and photographed) and at the Channel ports, but not much about airports.

The details are very sketchy at the moment, and it's not clear how much is media hype- but it won't be sooner than October.

No need for either right now, for what it is worth, you personally will not need to do anything ahead for EES, it is just a change to the entry procedure (going digital, unified across all Schengen Countries, so no stamps anymore). EITAS will be relatively easy, but another step for your trip, though it is valid for several years. Both seem to be far from certain for implementation.

It is hoped that all this speeds entry and exit.

You just need your passport for the moment and of course if asked evidence of financial means etc... although it's seem they only dig into the stuff with young people travelling alone who are more likely to not have the means, the insurance and intend to work illegally from what I have heard.