This is a challenging question on many levels. The first approach to take is to describe socialism's connection to land and labor. Essentially, socialism suggests that land and labor, elements that are privatized under a capitalist system, becomes publicly shared and held elements. The ownership of the means of production that controls both labor and land is held by a governing body or collective entity.
In terms of Socialism's in America today, this is a bit more nuanced. There are Socialist political parties that actively seek political power. Yet, I think that the Socialist relevancy to America today is its critique of capitalist theory. The idea of empowering workers and supporting laborers' rights is something that has been a part of American social theory and economic practice. If we examine the empowerment of workers under the Socialist theoretical foundations, we see that it appeals to much within American history. Workers, of which there are more than owners, demanding for equal treatment and equality in rights. This is an embedded principle in American society. The other element of Socialist ideas in American political theory is in its role of externally controlling bodies. A pure capitalist system trusts in the marketplace and believes in no government intervention. To rectify challenges in the market place, the capitalist idea of "the invisible hand" is invoked. This force of nature will rectify challenges on its own and government intervention is not needed. This is not the role of American government, and over its history, has not been its design. Throughout American History, its government has been a source of change and has presented the belief that it can help make things better for its citizens. Whether it was FDR's New Deal or Johnson's Great Society, President George H. W. Bush signing legislation to ensure that businesses adapt themselves for disabled and physically challenged individuals, or our current administration's bank bailout (actually initiated during the previous President's administration), American Government has taken the position that it can assist and help society. We see an external element taking control and intervening in the marketplace. While there is little chance of America "going Socialist" and even less to indicate that America is "socialist," the reality is that there are principles in the belief that public entities can positively intervene in private enterprise, which is a tenet of Socialism.