The excerpt clearly states that he obtained a Journalist Visa. In the absence of any evidence in the excerpt to the contrary, we can safely infer that he is a journalist.
He stated that he believes what his country is doing in Vietnam and goes on highlight United States' attempt to flush communist guerilla insurgency out of Vietnam.
<u>From the above points</u>, therefore, one can strongly infer that the author is a United States journalist who is convinced of the steps the Unites States government is taking in Vietnam.
The quote from "My Heart Is Bursting" most contributes to the assertive tone of Satanta’s speech is All the chiefs of the Kiowas, Comanches, and Arapahos are here to-day; they have come to listen to good words. I hope the answer helps.