I guess the letter should be read as a foreign policy document, (e.g. as evidenced by its wording devoid of nominal references to non-US stakeholders or other governments). As a general rule, the foreign policy of any country tends to remain constant, rather than vary, through the domestic political changes. The letter makes the US government oversight over ICANN better documented. I doubt the NTIA reply can add much explicitness, but we'll see.