I'm a German citizen, currently working in the US on a greencard. Other people here have already pointed out that the additional tax declaration will be a MAJOR time and money sink each and every year, even where there is nothing to declare. And given even the slightest complexity with retirement accounts, social benefits or investment or brokerage accounts turns this into a minefield that lead to sleepless nights.

Now, even worse, the US reporting obligations to non-US banks (FATCA) will make financial life in a foreign country close to impossible. When I communicated my US address and tax status to my German bank, they immediately notified me that they will have to terminate our business relationship as compliance to US tax law is too complex and too expensive for them. I searched around and contacted dozens of banks, but no German banks are willing to take in US residents. Even if you end up finding one to give you a checking account, it'll be close to impossible to set up any private retirement accounts, left alone brokerage accounts. In sum, your kids will be excluded from "regular" financial life as known by their peers and they will have to constantly navigate through that complexity, possibly facing jail time for the slightest misstep.