There is a limit to how hard you can push to collect tax dollars. A little too much pushing and the US will experience a severe brain drain effect as business persons move not only jobs overseas but themselves overseas. I am not saying it is right or wrong. Just stating what will happen...
The problem is that congress passed a law last year that states that they can collect income tax on US nationals for up to 10 years after they move out of the country, even if they denounce citizenship and/or have not set foot in the US for even 1 day that year. The US is doing the exact same thing Nazi Germany did--they are trying to make it impossible for its nationals to leave the country!