Per Wiki's own article, there are many countries (https://en.wikipedia.org/wiki/Gaza_genocide#/media/File:Inte...) that disagree with the genocide distinction. Those countries are not just the US - they are large and small nations from all parts of the world. Is that not the definition of highly contested?
The point of the editors is that it is long standing precedent on Wikipedia that the statements of politicians have little factual relevance except for the statement itself, so they are normally not taken into account.
There's also this big list of various professional opinions on the matter: https://en.wikipedia.org/wiki/Template:Expert_opinions_in_th...