

Doesn’t difficult very much depend on what you think matters? You’re instantly missing out on anything app, anything QR-code related (ordering food in some restaurants, links, etc.), membership cards that no longer exist in physical form. Some places sell certain tickets online only and then you may need a printer or you’re SOL. I’m sure in missing something so that’s not extensive.
But at the same time, if you have a dumb phone, you can still stay in touch with friends and family. You’ll be missing out on images being sent that are bigger than 2 pixels. But you wouldn’t be completely out of the loop. And if you have an internet ready computer at home or at the next door library, just not on you at all times, I think that’s crucial. Without that you’re ending up in all sorts of trouble.
I would say it’s doable if you are good at not giving F’s. If at the same time you only want to use cash or just no credit cards you’ll be making your life much harder though.
Germany is a collection of regions and former midieval fiefdoms that pretty much all hate each other. Munich and surroundings is representative of Munich, not the whole country. But a lot of the stereotypical things Americans think of when thinking of Germany will be there. Most of the South was occupied by US forces post WW2 and all the lederhosen, Oktoberfest, and Neuschwanstein Castle should feel just right for you. And that pisses off the Germans in the rest of the country like telling a Texan their BBQ is trash.
Somebody said Germans aren’t into smalltalk. That’s probably true by comparison to the average American but by comparison to their countrymen in the North they are positively chatty in Bavaria.
Bring cash or research at least two ways to get your hands on it while in the country. Just in case one method fails. A lot of places do not accept credit cards and that will probably extend to US debit cards that run on a cc system.
And yes, especially intercity trains are a clustereff of neglect and wear and tear and timetables are not to be trusted at all.
Don’t rent a car and just floor it on the autobahn. Take it at 120kph/75mph first for an hour before you put your pedal to the metal. Get a feel for the road and the rules first because Germans love a rule. And it decreases your chance of hitting a concrete pillar. No speed limit areas tend to be between cities, not on the built up areas. Know that speeding tickets will be charged after the fact or they will follow you by mail.
The staring people refer to here may be, to a large extent, that if there are no Chinese tourists in the area, American ones will be the loudest ones around, carrying their cute little fear of dehydration made manifest water bottles around. You look funny to us and we can’t help it. Don’t buy bottled water, tap is fine to drink. But there aren’t drinking fountains around. A lot of drinks in bottles and cans charge a deposit fee you’ll get back when you return the empty container to the supermarket - your kid will know the drill.
If you’re planning to cross borders be prepared for actual border checks. Our version of ICE crackdowns is making the federal police force delay EU cross border traffic with pretty much EU-illegal ID checks. We spend absolute millions of Euros, accruing a gazillion hours of overtime to catch two illegal immigrants or thereabouts. Political theater with waiting times for all.