If the value of US Dollar crashed the economy of the entire world will also down as most of the countries depend on USD and their economy may also depend on bitcoin therefore if the USD crashed it will effect all most all the economies of the world.
Nope I do think so, because if we see the crises in US dollars it would affect the USA region only. I think other countries would be safe I'm their economic balance. I think USA government may adopt the bitcoin that time make as the national currency.
It happend before. Most countries are affected when the when the price of USD go down. On bitcoin side, i think the bitcoin will go up since more user will convert thier USD to bitcoin.