Do foreign bitcoin exchanges need to be liscensed in every US state? I read something about this, but it seems pretty unenforceable. I understand US-exchanges need to be liscened as money transmitters in every state, but how can US states fine a foreign entity for making transfers to US accounts? What kind of laws are being broken?

As far as I understand, the exchange is only bound by the laws in the country which it does business and transfering money to US bank-accounts isn't exactly breaking any sort of laws. The US customers would still be coming onto the website, presumably hosted in the foreign country, so the business would still only be considered taking place in that foreign country. 

I'm no expert on the legality here of foreign entities. Can anyone offer some advice.
As CTO of Bit2C, Israel bitcoin exchange I can tell from my experience that the exchange has a bank account at it's local country, the exchange required by the bank which holds the customers funds to "know your customers" and in Israel we are obligated to ask from customers who make deposits to sign a document declaring they have no us citizenship, so we can't deal with US customers.