I thought only permanent residents and citizens of Japan can apply for the trusted traveler program (TTP, i.e., the automated gate) but I guess they have expanded the program to include more people (Immigratino Bureau of Japan link: http://www.immi-moj.go.jp/ttp2/en/outline/index.html). US citizens can apparently apply if they already have Global Entry so they don't need meet all the other conditions (especially the condition "O", which not a lot of people can meet).