The speaker describes a relationship with a boy who seems to embody the "all-American" type: green eyes, easy laughter, a contentment that feels careless. She plays on the cliché of "American as apple pie" to suggest he is more image than person. His kisses are "two dimensional," and the speaker feels pressed "flat" beneath him, as if she is turned into a drawing herself. The line "Cartoons can have mass" is the turning point, because it admits that something shallow can still weigh on you and erase you.
The speaker feels diminished, exposed, and unreal, caught inside a "warped American dream" she doesn't fit. When he quietly asks "How do you live?" she has no answer, and the poem hints that her silence is loud. The ending is chilling in its flatness: he says "I love you," and she repeats it back. The mood is numb and uneasy, and her reply sounds less like love than like a script she has been handed.