I'm not sure if this comment will be high quality enough, but we covered this pretty well in one of my political economy classes. The main reasons presented by Dr. Melanie Kolbe of the Graduate Institute of Geneva were:

1.) The lingering of the Haymarket Square bombing on the American conscious. The late 1800's were rife with nationalist sentiment against foreigners, anarchists, and communists, who were often viewed as one in popular thought.

"The mainstream media and trial attorneys invoked a narrative of American nationalism in order to imagine the Haymarket anarchists as the dynamite-wielding leaders of “an incendiary and alien rabble.”58The stridency of this rhetoric is implicated in long-term patterns of American xenophobia over the course of the nineteenth century" [Clymer 2002]

Socialism became viewed as anti-American, and this allowed for detractors of socialism to frame discussions of class strife as distinctly traitorous, violent, and destructive to society.

2.) Following Manifest Destiny, there was a very low population density in a lot of the Central US. This directly contrasts from the harsh inner city conditions that triggered Socialism in Europe. Because people could just go get a farm, they had an alternative outlet to socialism for a long period in America's formative years. Stiglitz argues that this created the conditions necessary for the productivity shocks in agriculture that led to gluts in the labor market prior to and during the Depression.

3.) To an extent, I think that socialism did catch on. Garraty 1973 suggests that the economic response the US took to the depression was comparable to the German National Socialist response to a poor economy:

" CONSIDER FIRST how the two governments dealt with poverty and mass unemployment. Both combined direct relief for the indigent with public- wvorks programs to create jobs. The Americans stressed the former, the (Germans the latter, with the result that while acute suffering was greatly redticed in both nations, tunemployment declined much more rapidly in Germany. Congress appropriated $3.3 billion for public works in 1933, l)ut Roosevelt, unconvinced that public works would stimulate the economy and fearful of waste and corruption, did not push the program. Briefly, during the winter of 1933-34, he allowed Harry Hopkins to develop his Civil Works Administration, wlhich found jobs for over four million people, l)blt in the spring the program was closed down to save money. Only in 1935 did federal public works become important. Then, under Hopkins's WVorks Progress Administration and Harold L. Ickes's Public Works Administration, countless roads, schools, bridges, dams, and public buildings were constructed.4"

While the US didn't carry out such atrocities as the Nazis, their economic response was heavily reliant on state intervention, to a degree many today would consider to be socialist.