Mind you, that was all the defense the White House could muster anonymously. Nobody was willing to even put their name to that pretense, and for unspecified reasons Politico decided that transparent spin effort was worthy of anonymity. (Nobody in the entire story was willing to go on record to describe it, in fact, a sign of the eggshells every member of government must walk on to avoid being written into Trump's ever-growing enemies list.)
“Although the United States did not nominate a candidate this year for election to the committee, that in no way diminishes our global leadership on efforts to eliminate racial discrimination,” [a senior Trump administration official] said.
That said, it sounds suspiciously like Press Secretary Sarah Sanders, a particular aficionado of the "even though we did the bad thing, actually we stand for the good thing" talking point.
The background story on this one is intriguing. The current U.S. committee member is Gay McDougall, a human rights lawyer picked by President Obama. The White House apparently couldn't stomach renominating McDougall, apparently due to the Obama connection, but also couldn't rally the competence to come up with any other name. So they just bailed on the whole thing.
That's been a familiar tune throughout Team Trump's stumbling staffing efforts; it's never quite clear if Trump's assemblage of trolls and sycophants are leaving large swaths of the government empty as orchestrated plan or because they simply lack the base competence to do it. You can probably put this one in both columns.