Another example of too many confusing government abbreviations. There are two NSAs at play here:
National Security Advisor: This is the job title held by McMaster. This NSA lead the staff of the National Security Council which provides advice to the president on issues of national security and foreign policy.
National Security Agency: This is the intelligence gathering entity you're thinking of.
The two NSAs, while both have a role in national security, are distinct.
Thanks!