Officer of the United States
An officer of the United States is a functionary of the executive or judicial branches of the federal government of the United States to whom is delegated some part of the country's sovereign power. The term "officer of the United States" is not a title, but a term of classification for a certain type of official.
With a limited number of exceptions, all officers of the United States are appointed by the President and are subject to the approval of the Senate unless it chooses not to require such approval. Civilian officers of the United States are entitled to preface their names with the honorific style "the Honorable" for life; though in practice, this rarely occurs.
Officers of the United States should not be confused with employees of the United States; the latter are more numerous and lack the special legal authority of the former. https://en.wikipedia.org/wiki/Officer_of_the_United_States
US Code Title 18 is very specific throughout when referring to
"....Officers, Employees, and Elected Officials of the Executive and Legislative branches.." [esp Pres. & VP]
And are not referring to the POTUS in 18 U.S. Code ? 372 - Conspiracy to impede or injure officer
or that Federal jurisdiction supersedes TX State law in the removal of this body in 1963...
That's from a Wikipedia article. I reject it as unreliable.
Here's something that you probably overlooked in the Memorandum for the Attorney General:
Objection to the multifaceted conspiracy bill, of which this provision was a part, centered on its application to conspiracies to overthrow the Government of the United States; It's important to keep that in mind.
The President is the Chief Executive Officer of the United States as well as the Commander in Chief. Your argument is silly. However, if we were to assume for the sake of argument that he was not, strictly speaking, an Officer of the United States, the removal of JFK's body from Dallas would still be covered under 18 U.S. Code ? 372. As the Memorandum for the Attorney General noted, the terms "office" and "officer" have broad readings.
The term "officer",appearing in 18 U.S.C. ? 372 includes both permanent and temporary, full- and part-time officers and employees of the United States.