It's like denying the holocaust when the internet exists and videos of it are out there and you can see it happening right in front of your eyes.
Europe is aiding in the genocide as well, especially Germany, the Netherlands and the UK. Though you are right there are still countries like Ireland, Spain and Belgium that at least call for ceasefire.
The map looks very similar to others during the cold war (US supporting apartheid, a variety of dictatorships and colonial movements and genocidal regimes) yet, you don't really see anyone asking how the US people let that happen.
In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
Killing members of the group;
Causing serious bodily or mental harm to members of the group;
Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
Imposing measures intended to prevent births within the group;
Forcibly transferring children of the group to another group.