Language, including its structure and vocabulary,  is intimately related to the culture,  or rather, to  the content it expresses.   for example, we don't  have  problem to  discuss physics or IT with American,  because  we are familiar and confident  with those issues we talk about,  together with the concrete language associated.   We  have also spent our most time on those scientific and technical problems as we have to.

Beyond that,  as the first generation, our culture life mainly is still that of Chinese,  or  at most, that of Chinese American.  It restricts what we can talk about fluently and idiomatically with our second language.  It is probably better,  though,  when we write carefully  because we can correct our writing back and forth.