MacOS bootable not a like window bootable, something change below down you can learn about how to make macOS bootable usb drive
In macOS, the option to create a Windows flash drive appears only when the computer does not have an optical drive. If your Mac has an optical drive, the option will be either missing or grayed out
1. From the Finder, open the Applications folder, and then Utilities.
2. Open the Boot Camp Assistant, and then click Continue. The next screen should give you a list of options.
3. UITS recommends making the USB drive installer first. You don’t need to install Windows or download the support software at this time, as it will be easier to do both later. To proceed:
a. Verify that the USB drive you will be writing to is plugged in.
b. Uncheck the Install Windows 7 or later version and Download the latest Windows support software from Apple options.
c. Check Create a Windows 7 or later install disk and click Continue.
4. Your USB drive should be listed in the “Destination disk” area. Use choose to browse to your .iso file; after selecting it, click Continue.
5. If prompted, confirm your action and/or provide an administrator password. The process of writing the .iso file to the USB drive can take 20 minutes or longer.