People should question the USA every time they talk about South American countries. The same as how people question China or Russia when they talk about bordering countries. Super power will do what they can to influence other countries and historical and recent events make it clear that the USA is willing to lie and defend its lies. So people have the right to not believe the USA.
Sure. When it's appropriate. But it isn't appropriate here. There are third party organizations with no love for the US also making statements about this.
It's not whataboutism, it's good to look at the history and motivations of anyone making claims like election fraud. US officials are saying it's fake, the US has a long history of South American political interference, especially if there is even a hint of socialism.
I don't think they are staying Maduro won. Polls showed this was going to be a landslide against him. Can't trust polls especially in a dictatorship but I think there's something there. I know in my heart he lost.