First, not everybody here in the US are selfish.  Not even close.

Second, based on your interaction with few people who might have, in your opinion, acted selfishly, does not mean the who Nepali diaspora in the US is made of selfish people.

Third, you might perceive others to be selfish but in reality it might be because of the resource constraint - be it time or money or both. 

Just my two cents... uh... make that three.