Many Chinese Americans have been here for generations, since the 1800s. Few Indians lived here before 1950. Ease of assimilation doesn't explain it.

Many Chinese Americans, sure. But how many in relationship to the Indians ?

There are more 2nd+ generation Chinese Americans than all Indians combined. Indians are a tiny and recent immigrant group.

But my impression is that Chinese Americans are pretty much white biologically and culturally by the third or fourth generation because of the high rates of interracial marriage.

And specifically one aspect of it - language. English for Indians is like a first language.

And being myself from USSR, i think there is another cultural aspect - that coming from former socialist country impact Chinese somewhat similar to how it impacts Russians.