Change currencies through BitCoin or other Cryptocurrency
With no bank account: You can buy Bitcoin in your home country then sell them for cash in person in the US through sites like Local Bitcoins once you get to the states.

With large sums of money its good practice to wait for six blocks on the blockchain before considering the transaction confirmed.

With a bank account: Non-U.S. citizens are allowed to open a bank account in the United States. You can wait to open a bank account in person when you arrive or try opening a bank account in your home country at a bank that operates in both your home county and the US. (In Brazil HSBC is one example of a bank that operates in both counties). 

To sell your Bitcoins get an account at an exchange like Coinbase or Circle, trade your Bitcoins for USD there and connect that with your US functional bank account to withdraw the funds.