Ref: Here I try..

 

The speaker of ... Saverin says that Saverin gives up US citizenship is not because of his disaggrement/disapointment to US; only that the over-complicated rule to the oversea properties of citizen's.

--> 好象語法上不通，"is not" 沒有主語？ 另看下麵的"because of"的用法。

The speaker of ... Saverin says that Saverin gives up US citizenship is not because of his disaggrement/disapointment to US; only that  but the over-complicated rules to the oversea properties of citizen's. citizens.

 

because of

: for the reason of
▪ The picnic has been canceled because of [=due to, on account of] bad weather.▪ Because of this [=for this reason], only very rich people can afford to live on the island.▪ Because of you, we missed the bus. [=you caused us to miss the bus]▪ The accident happened because of [=through] carelessness.

Source: http://www.learnersdictionary.com/search/because