Abraham Lincoln is not just a vampire hunter. He's a standard and well-recognized hero for many Americans. In “O Captain! My Captain!,” the speaker has an intense amount of admiration for his captain, a stand-in for President Lincoln. Back on land, the people share in the speaker’s admiration and cheer the ship into the harbor. What the captain has done specifically to win everyone's admiration is never really made clear in the poem, but we do get the end results of his admirable actions: he's steered through rough seas and sacrificed his life to ensure the safety of the ship.
The sailor seems to admire the captain as though the captain was an ideal, masculine father, kind of an anti-Homer Simpson. He implies that the captain was stern but fair and emphasized hard work and success.
The speaker’s admiration for the captain is different from that of the people on shore. The speaker has witnessed the captain’s actions first-hand and has seen the captain overcome difficulties and errors that those landlubbers on land did not see.
A patriot is not just some guy who is good at football. It's a person who loves their country so much that he or she would fight to protect the rights and freedoms that the country values. In “O Captain! My Captain!,” Whitman celebrates the bond that patriotism creates between the average citizen and the leader of the people. The captain is portrayed as a patriot who has risked his life in some mission for the people on shore. The masses on shore celebrate the captain's success, and the ship’s return, with all the trappings of patriotism: flags, bugles, and bells. (Remember that this poem is set before American flag lapel pins were invented.)
“O Captain! My Captain!” is a star-spangled, patriotic poem, rather than a flag-waving nationalistic poem, because the poem presents a general feeling of love for one’s country, rather than a loyalty to specific ideas about enemies, allies, or the rights of citizens.
The poem is not distinctly American in the sense that just about anything in the poem could apply to any country in the western hemisphere in the mid-1800s. But the exact context in which the poem was written (the assassination of Lincoln) does make it an “American” (not a vampire) poem.
More than 620,000 people died in the Civil War, and that doesn’t include the overall suffering that the war created. The Civil War doesn’t really come into the story of “O Captain! My Captain!” except as it's represented by the ship’s voyage. The suffering in the poem is mostly concerned with the death of the captain. More specifically, it is about the speaker’s suffering over the loss of the captain, his total BFF and personal hero. The contrast between the speaker’s private pain aboard the ship, and the people’s boisterous behavior on the shore, brings into focus how it’s much easier to understand suffering on an individual, rather than a group, level.
“When Lilacs Last in the Door-yard Bloom’d” is a more personal poem because it presents detailed images to the reader, along with the speaker’s feelings toward those images (plus it has flowers in it). "O Captain! My Captain!" leaves out too much detail to be as effective.
We never know how the captain dies because Whitman wrote and published the poem at a specific time when everyone knew exactly what had happened to Lincoln. Nobody needed cluing-in on the backstory.
Macho, macho man. Whitman was obsessed with the idea of masculinity. He associated it with work, war, citizenship and politics, and stern father figures. “O Captain! My Captain!” seems to throw these all together in a blender, then pour it all into one intimate relationship between a sailor and his captain. Many scholars today recognize that Whitman himself was gay, but that doesn’t mean that the captain and the speaker are lovers. However, the relationship is indeed intimate and emotional. The speaker has a tremendous love of the captain and that bond was fairly typical of men before popular culture made it "unmanly" for guys to share sensitive and emotional feelings with each other. Notice how the speaker sees the captain as a father-figure. Is this the result of their journey together or is it something deeper?
The mention of body parts like the arms, heart, and lips make the scene a sensual one that excites the senses and makes us look more closely at the relationship between the captain and the speaker. It might be just a sailor-captain kind of thing, or there could be something else going on here.
Because the speaker calls the captain “father,” we as readers can assume (with no other information than how good fathers were portrayed in other literature from the 1800s) that the captain was fair, stern, emotionally distant yet compassionate, and decisive. Think Tom Skerritt in A River Runs Through It.