I think the key to understanding this is to remember that it was written by the NSA for the understanding of the NSA, or other highly authorized eyeballs in the government.
In many government documents, use of the name "U.S." is shorthand for the U.S. national government, not the entirety of the nation. Sometimes it is even shorthand for the particular agency that authored the document (since, in theory, they represent and act on behalf of the entire nation).
So what this internal NSA document most likely means by "unrestricted access and use" is the NSA's unrestricted access to, and use of, whatever data they want.
Think of it like a budget justification (since that is the purpose of at least half of all internal government reports). "You need to keep spending a lot of money on this program if you want us to keep getting all that data you like so much."
In many government documents, use of the name "U.S." is shorthand for the U.S. national government, not the entirety of the nation. Sometimes it is even shorthand for the particular agency that authored the document (since, in theory, they represent and act on behalf of the entire nation).
So what this internal NSA document most likely means by "unrestricted access and use" is the NSA's unrestricted access to, and use of, whatever data they want.
Think of it like a budget justification (since that is the purpose of at least half of all internal government reports). "You need to keep spending a lot of money on this program if you want us to keep getting all that data you like so much."