The whole thing is still NOT CONFIRMED.
Here is how FOX NEWS REPORTS IT:
Sources who had debriefed two former members of Bergdahl’s unit told Fox News Bergdahl left behind a note the night he left base in which he expressed disillusionment with the Army and being an American and suggested that he wanted to renounce his American citizenship and go find the Taliban.
U.S. military officials would not confirm the existence of the letter, but if it does exist, it would likely be part of the original file on the investigation into Bergdahl’s disappearance.
This is to explosive for them to put it on without not getting it confirmed.