> It's a problem every European country faces (work in France, live in Germany for example) and still none of them motivate their citizens to abandon their citizenship when they live abroad.
What I'm saying is that it is practical and pragmatic for the US to have this law. It's not for Germany. Why? Because the number of immigrants in the US is extremely high.
Was US to implement the same law Germany has then 60% of New Yorkers would be able to avoid paying income tax in the US. Not that all of them would do that, but just saying. US has this special circumstance of having a big chunk of their population with 2 passports. Not 10% like in Germany, but 60% like in New York. Then you have to enact a law to discourage people from taking advantage of their 2nd citizenship in terms of taxes, or nobody would pay, they would just stay over 6 months in their mother countries whenever that's convienenient (i.e. reaching retirement age).