In fiction, "the Gothic" refers to a set of tropes first popularized in the second half of the eighteenth-century. Gothic novels, which remained popular well into the mid-nineteenth century, often featured some combination of the following elements: mysterious secrets, a threatened or persecuted young woman, a villainous male figure (usually an aristocrat) scheming to seduce or trap her into an unwanted marriage, the possibility of ghostly or supernatural elements, hints of perverse sexuality, and family members who betray their proper roles as guardians. The first wave of Gothic novels by English authors were almost always set outside of England in countries like France, Italy, and Spain, where the Catholic religion was the dominant faith. Catholic traditions such as nuns, monks, and convents often featured in these novels, but usually to perverse or evil ends.
By the time Henry James was writing, many of these Gothic elements had shifted and evolved into different forms. For example, the "sensation novels" that largely dominated the British publishing market in the 1860s relied on some of these tropes of illicit secrets and the dark side of domestic life integrated into seemingly everyday English households. James was well aware of both the history of Gothic tropes, and the more contemporary literary taste for recognizable settings. He made use of both in The American, drawing on this literary heritage so as to highlight the cultural gaps and tensions between Europeans and Americans.
The first wave of Gothic novels had largely been used by English writers to explore their xenophobic anxieties about Catholic countries in an era marked by war between Britain and France. James was far less prejudiced but also drew on stereotypes by introducing Gothic elements. Rather than stopping at the social realism in which the Bellegarde family are merely snobs, he makes them potentially murderers and possibly invested with supernatural powers of killing through force of will. Claire's entrance into the convent, in keeping with Gothic tradition, is presented as a terrible place where she will effectively be buried alive, suggesting that Catholic customs are barbarous and repressive, especially towards women. The idea of the female domestic who, due to her position, has access to information and secrets, has ties to both the Gothic and sensation novel traditions.
James's fiction would be marked by an interest in supernatural and ghostly elements throughout his career, perhaps most notably in his novella The Turn of the Screw (1898). However, The American is the novel most closely allied with the Gothic, allowing him to link his contemporary criticism of the European aristocracy with an earlier tradition of similar doubts.