"Dear Mr. President" is meant to envision the U.S. President(s) who ... viewer admires most ... Nor is it about the political aspects, but about what a leader of the USA did ... thinking of what was best to safeguard America and fellow citizens against future attacks and the difficult decisions to send troops in harm's way.
And while every President must deal with political consequences, it should never impact decisions that weakens America's ability to protect and react against national security issues ... like Presidents Franklin Roosevelt and George W. Bush had to face daily during their tenures after devastating, deadly attacks to our beloved USA homeland.
Then there is all that President Abraham Lincoln had to deal with during the civil war!
My youngest son was serving in the Marine Corps when the attacks on September 11, 2001 occurred ... and served in Iraq during 2003. Presidential decisions become even more important when they impact a family member, who is ordered into harm's way ... even if ... it is willingly done with extreme pride and resolve.