Hi there, as for the tool allowing you to open a BitLocker encrypted USB on a Mac, iBoysoft BitLocker for Mac is the best. It gives full read-write access to BitLocker-encrypted HDD, SSD, USB flash drives, SD cards, etc.
Feel at ease using this wonderful toolset on your Mac to open the BitLocker encrypted on your macOS computer.
If you're eager to open the BitLocker encrypted drive on your Mac for free, you can install Windows on your Mac via Boot Camp.
Take care~