Why was the soviet union not affected by the stock market crash

Assuming that you're referring to the stock market crash during the great depression,

I think it's pretty much because Russian economy is very secluded back then and they did not involved in any major foreign trade.
During that time, they still use communist-based economy and very little free market corporations wanted to deal with them and visa versa. 

Apresident can veto /reject a bill

Ithink it’s bill gates.