Booting iMac8,1 off USB


I am having some trouble booting my iMac off ANY USB with any OS. My DVD has been replaced with SSD from which I'm running Mac OS. My original HD I use for data.

Is this a problem with old machines? Or am I just doing something wrong. I just cannot boot my BOOTCAMP created USB. I've tried many bootable USB creators with different options, so I don't think that's the issue.

The symptom is always the same. I press opt key, I see my USB as "EFI". When I select and hit ENTER, it hangs. Mouse freezed. Nothing. No error or anything.

If someone can at least let me know if I'm wasting my time.
I've seen claims to be able to boot to a Boot Camp partition on an external drive, but I was never able to replicate it.
I has everything a 2020 version video to show how to use an SSD external for Windows on Intel Mac!