The Holodomor may not be officially recognized by the US government as a genocide, but I believe that is mostly clerical. In December of 1985 a bipartisan commission was created by several members of the House and Senate with the goal in mind of educating the American public of the unfortunate events in the Ukraine. This was called The U.S. Commission on the Ukrainian Famine (simple, right?). The Commision released its findings in April of 1988 with the conclusion that the famine was a man made genocide committed by Stalin's government (among other things).

On top of that, in 2003 the 108th Congress released House Resolution 356 (which you can find here https://www.congress.gov/bill/108th-congress/house-resolution/356/text), which acknowledged that the famine was man made by Stalin's government and was a heinous act of mass murder, though the word 'genocide' was not specifically mentioned.

H.R. 356 also acknowledged that American journalists actively suppressed knowledge of the events leading up to the famine in order to prevent Soviet criticism. The specifics for that I am unsure of, but considering that the United States had moved to officially recognize the Soviet Union in 1933 it may have seemed more pertinent to keep the Soviets as allies rather than vilify them.