You can try reconnecting your USB drive to your Mac. Although your computer has recognized it to be read-only, may be there some bugs during the operating system communication with the external device. So, just for a trial, simply eject the USB and then connect it to another port on your Mac slowly and tightly.
If it is useless, go to Disk Utility to run First Aid to check and fix the possible tiny errors on the USB drive. Is the USB drive still read-only on your Mac? I want to learn that when you formatted your USB drive as Mac Journaled, which partition scheme did you choose? GUID, MBR, or Apple Partition Map? This matters a lot.
Although you can select any one of the three for your external storage device if you only use it for data storage, GUID Partition Map works better on all Mac computers, MBR is mainly for all Windows computers, and Apple Partition Map is compatible with old PowerPC-based Mac machines.
If you selected an improper partition scheme, you have to reformat it. I know you don't want to lose data. You can get files off the read-only USB first before formatting.
Besides, you can right-click the USB and select Get Info to see if there's an "Ignore ownership on this volume" option. If there is, check this option to see if it can make the USB drive read-write on your Mac again.