Sure, they are the only ones, but does that mean it's morally or logically wrong? Theoretically a government spends a certain amount of money on each individual as they live, become educated, and work in the US. If they decide to leave the US to work abroad, they shouldn't get any tax revenue back from you? They do allow you to deduct taxes paid to your residence country.
Taxing is mainly to pay for the facilities that the Government is providing you currently. That is the reason why vast majority of the countries (99% ?) are taxing based on physical presence. So if you are out of the country for most of the time during the last year, then you don't pay tax.
US is immigration based. 60% of New York City population wasn't even born in the USA. Wouldn't you think that in this circumstance a substantial number of them could avoid taxation by living more than 6 months abroad even though their income would be generated in the US? I'm a dual Polish/US citizen. Easy scenario: remote work in US for $100k+ a year while residing all that time in Poland. That's why they have it. There is no other country in the world that's that rich and is based on immigration, so people would have incentive to game the system. That's why the system is built that way that you have to _declare_ your income even when abroad. If somebody can't do this because of $3k lost, that's just shows for them not for the US.
That's a problem, but it doesn't have anything to do with citizenship. Rather with residency vs. place of work. 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.
I am a German living in the US and I have no downside of being a German citizen. As a green card holder the only thing that I cannot do is vote. It would be nice to become a US citizen one day, but given the huge downside of the tax burden if I ever decide to ant to live somewhere else for a while is a big deterrent for me.
