If you have Bitcoin in your account, you should be able to send Bitcoin to an address. If your currency is no longer Bitcoin, then you cannot send Bitcoin at all and it will have all been converted to whatever currency you set.
Scam alert! You cannot buy bitcoin at Circle any longer. If you 'deposited money today' - you don't have any Bitcoin to send.
That's not true. You can still deposit Bitcoin if your account already had the Bitcoin currency option set. So long as your account has the Bitcoin currency option set, you can still send and receive Bitcoin.
I'll tell you what, just send me a PM with your private key and I'll transfer your Bitcoin to your CoinBase wallet for you.
AFAICT Circle does not give you access to the private keys.