You are right.Guam is Unincorporated Territory of the United States and US entry visa is required.I have confused it with CNMI.Sorry.But still, there is no firect proof that US visa is good for CNMI.

• 非常感谢各位的详细的讲解，现在的问题是，我持有美国签证，是必须从美国本土去塞班可以免签，还是说只要在签证有效期内，我可以从中国大陆直接去塞班而不先去美国本土呢？