I'd be curious to hear what you think is missing from the culture of Indians/Bangladeshis/Pakistanis that would preclude them from becoming part of an "egalitarian western democracy"?
That culture, in turn, isn’t about superficial stuff like food and language. Who wouldn’t think Indian food is a good thing? But what’s important to maintaining and perpetuating a democracy is deep culture. How do people in a culture view relations between people in society? On the sub-continent, we have an intensely hierarchical view of society, where we place great importance on people’s breeding (coming from a “good family”). Family ties and personal relationships, moreover, are much more important than abstract rules. People are much more willing to cover things up or bend rules to protect personal relationships than in the west, making the sub-continent a breeding ground for corruption. Asians, in general, come from societies that had millennia of large-scale imperial government. So the view of the relationship between the government and the individual is very different.
I'll give you a concrete example of the distinction. My family easily assimilated into the Virginia town where I grew up. That only means we can function—very successfully—within an environment where the norms are imposed by some other culture. We couldn’t recreate that environment. My mom can function in a society where norms of egalitarianism are imposed by a dominant culture. But that’s just not how she sees the world. She looks down on "the common people" and think that society should be governed top-down by people of good breeding and education. Because that’s a foundational assumption in our culture. And if suddenly 20% of the population were like my mom, the environment would become less egalitarian.
In fact, that's exactly what happened to my town. We went from being a quintessentially American middle class town to having a large number of affluent, educated Asians move in. And they completely changed the environment.
The second generation Asian Americans I know aren’t quite as hierarchy-focused as say my parents. But they’re also nothing like my wife’s Oregonian family that’s been in the US for hundreds of years. (Among whom having status is almost something to be embarrassed about.)
The only argument against this is to say that well "that's xenophobic". But I think this is just a way of ending the points made without discussing them because they cause discomfort. There are benefits to immigration but those benefits are not distributed evenly. It's also hard to benefit from immigration materially and politically but simultaneously say it's being done for humanitarian reasons and anyone opposed is just a bigot. It's easier to shut down debate than have to confront this.