If Obama does this without a UN Security Council resolution, there is no way to predict how Russia and China will react. America will have declared itself to be an official 'rogue state', the same kind of rogue state America has attacked time after time.
This ani't Libya, Iraq, Yemen, Afganistan, Balkans, or some craphole African country. This is a modern State with a lot of powerful friends. This is whole different game than America is used to.