It is my understanding, and I could be wrong, the purpose of the seg account is to keep customer funds separate from the funds of your FCM. I expect your FCM has only 2 Seg Accounts with a journal entry as to what is yours. One for futures in USD and one for foreign transactions.
I don't know if they have separate omnibus accounts for domestic/foreign customers... but the principle of "customer funds segregation" is supposed to mean that even if the FCM goes bankrupt, cutomer accounts are still intact.