The plot of Visit to a Small Planet centers around an alien named Kreton who unexpectedly arrives at a suburban home in 1957 America. He announces his plan to start a global conflict simply for his own entertainment, causing the other characters to reveal their political ideologies and values. Kreton showcases his telekinetic abilities by making all the guns on Earth float for fifteen seconds, which leads General Powers and Roger Spelding to suspect the Russians are behind it. Roger tells his television audience that the Russians have "developed a new anti-gravity technology that lifted all rifles in the free world about fifty feet into the air." He adds that "later this afternoon... Moscow, in an apparent effort to shift blame, accused the United States of raising all the rifles in the Communist world to a height of one hundred seven feet." Following this, Powers asks Kreton to let the United States publicly announce his existence, hoping it will "maximize positive publicity" for both him and the nation. These events highlight how Vidal satirizes the US-Soviet tension and the pervasive American fear of Communism during that era.

Hints of political paranoia are evident during Kreton's interview with Powers. The General cautions the alien, "you'll die if it turns out you're a spy or a hostile alien or something like that," suspecting that Kreton might be part of an "alien race sent here to study us before an invasion." However, Kreton is indifferent to mundane concerns like land conquest, and his laid-back attitude only further irritates Powers. Later, Powers informs Kreton that he is now "classified as a weapon" and that the Pentagon requires a detailed list of his "powers." Visit to a Small Planet critiques politics by revealing the insincerity of its leaders. Vidal depicts politics as primarily a stage for ego-stroking and personal gain. Ultimately, Vidal's play urges audiences to recognize the fear and suspicion that dominate modern politics while also highlighting what he sees as the irony in the phrase "military intelligence."

Vidal intricately weaves political themes with an exploration of patriotism. Although Samuel Johnson famously called patriotism "the last refuge of a scoundrel," Visit to a Small Planet delves into how different people perceive the idea of "love of one's country."

When General Powers initially suspects Kreton of being a foreign emissary, he tries to prove his patriotism by declaring, “if your people are thinking of an invasion they should know that we're ready for them. We'll fight them with everything we've got. We'll fight them with the hydrogen bomb, with poison gas, with broken beer bottles if necessary. We'll fight them on the beaches; we'll fight them in the alleys." Powers equates "patriotism" with military might, believing his fierce loyalty to America will scare Kreton.

As Kreton's threat of war becomes more plausible, Roger suggests Conrad enlist in the Army. However, Conrad refuses, stating he "doesn't want to fight anybody." His pacifist stance starkly contrasts with General Powers's aggressive display of nationalism. This surprises Kreton, who inquires, "Do you love your country?" When Conrad affirms his love, Kreton offers his own take on American patriotism: "Then don't you want to slaughter its enemies?" Upon Conrad's refusal, Kreton comments, “that’s the wrong answer. That is not a proper mid-twentieth century sentiment." Through Kreton, Vidal highlights Conrad's pacifism, arguing that not all patriots or "good Americans" equate "loving one's country" with a desire to "slaughter its enemies." Kreton tries to stir patriotic zeal in Conrad by singing old military songs, and when that fails, he references cultural icons: "Davy Crockett stood by his guns! Remember the Alamo! Remember the...