As with the similar case of Harry and Meghan, the media is missing the real story here! The truth is Japan is imitating Perfidious Albion's strategy of creating a situation where there will be a child who can simultaneously become president of the United States and monarch of their country.
Mako and her husband are moving to the US. When they have children born in the US, those kids will be "natural born" US citizens, and thus eligible for the presidency. Eventually, one of them can run for president, and ALSO become emperor, thus bringing the US under the rule of the rejuvenated Japanese empire. Yes, Princess Mako has technically given up her royal status. But that's just a diversionary maneuver that can easily be reversed when the time comes (much like Harry and Meghan's son being denied the title of "prince").
You heard it here first! The 2060 presidential election will surely be a contest between one of the children of Harry and Meghan (who could become King or Queen of England), and the child of Princess Mako (who could become Emperor of Japan). The British and Japanese empires are angling to take over America. The only question is which will ultimately prevail!