Then why not say ncle instead of uncle, and if its one of those words with a silent U, why does 'american' english drop it in many other words but not this one?

Here is my thoughts on the topic. I am from eastern Canada and I hear both "ont" and "ant" and also hear equal amounts of of people criticizing each other based on their way of saying it.

I have a feeling that it was originally "ont" and originated in the United Kimgdom, just like other words with 'u' that aren't pronounced like 'colour' and 'neighbour'. But if that is the case, why do Americans still spell it with a 'u'?

I myself say "ont" since in both Canadian/British English and American English spell with a 'u'. Americans... make up your minds :p decide on if your spelling includes silent U's or don't use them at all.