How can I get the USD balance in my portfolio using ccxt

I am using ccxt with python and am not able to get how much USD I have in my account.
Using fetch_balance USD is not listed. Using fetch_currencies I get USD but without any balance.
Using fetch_account ,which actually has a key “available_balance” that reports the amount (“value”) you have, again USD is not listed.
I tried one of the solutions from other similar situations reported like checking in my api if the USD wallet had been activated but didn’t find any USD wallet checkbox.
thanks for any help