> The U.S. ranks twenty-eighth on the Q.N.I., behind nearly every E.U. country. Kalin told me that the U.S.’s rank is partly due to its restrictive immigration policy, and partly because “there are so many weapons, and a high incarceration rate.”

Why does the fact that there are "so many weapons, and a high incarceration rate" make the US a bad place to live for millionaires?

There is a lot of subjectivity here. If you want to live in America, then an American citizenship is the most important one to have. However, if you want to live abroad, an American citizenship is terrible because you still have to pay income tax no matter where in the world you are.

(I do like measuring travel freedom though!)