closed by who? if it's not by their local jurisdiction, they cannot be closed america if you think so, they are out of the law of america
All the countries have laws regarding to financial transactions and they require a financial license for the Bitcoin exchangers. It doesn't matter if you are in USA or China.
this may be not true for crypto currency and probably it's not true by an amount limit, maybe those exchange are moving a low amount of money and they are not require any licence?
also are you sure that in all countries you need a licence for money trasmitting?