I think he meant to write "not unimportant". His proofreading isn't perfect and he has typos or missing words in a lot of his work. I'm a fan of the work itself.

The typo is fixed now.

Trying to parse the whole sentence, especially the "but" afterwards, the most reasonable explanation is that there is a "not" missing.

He's speaking from a military, America-first perspective (which I suspect may be somewhat affected, because he is hoping to convince people who sincerely think that way). The people in these countries are not strategically important.

He emphasizes relative importance, he doesn't claim that the actual people are not important.