"Maybe it's the Singaporean culture that you don't communicate with your peers at work, I don't know?"

No, it's not.
It has absolutely nothing to do with my country.
You have no evidence to prove that.
When you can't seem to find the origin of my apparent "lack of communication" skills, don't take the easy way out by saying it's my country's fault, cause it really isn't.

And don't ever say "Maybe it's an Asian thing, or maybe it's a Singaporean thing"
You don't know any better.
You've only been here for 3 years.
If you can't get used to "Asian or Singaporean culture" then get lost.

In school, we are encouraged to speak up, to voice our opinions.
Perhaps the reason why I don't do so / do much at work is because
You literally don't let my colleague and I complete at least 2 sentences before cutting us off completely.

Why not I phrase it this way?
"Maybe it's European cockiness that you behave so, I don't know?"