so this: https://cdn.netbsd.org/pub/NetBSD/NetBSD-11.0/images/NetBSD-11.0-amd64-install.img.gz
did you gunzip it before you dd'd it to the usb? :')
when you boot into the usb, all you should be getting is
- "press 1 to install netbsd"
- "press 2 to drop into a shell"
or something like that, i don't remember exactly