According to most state laws, it is not legal for a company that is not a licensed US real estate agent to receive a referral fee from a US broker.
If the non-US company in question has a real estate license in one of the 50 states, then you can agree on the referral fee with them individually.
Generally, the laws are fairly stringent about who can and cannot be paid a commission. This is to protect consumers from having their information sold and then failing to know who stands to benefit from a given transaction. The laws also serve to help eliminate potential conflicts of interest that may arise.