Imagine 3 excited kids (plus their friends) running around a room and something protuding out of the tvbox. I give it 1 month before they break the adapter and the usb that is plugged in
Rather, I would be more afraid the TV will be damaged, because that is a little more expensive than a TV box or wifi adapter.
It seems a bit of an excuse...
I have a suggestion to reverse the situation: put in an older router (e.g. 802.11g) in bridge mode that communicates well with the box.
Forget the WAN side, connect the network cable to one of the ports on the LAN. Turn off the DHCP server and set up the wlan interface.
Finally, connect the box to this router via WiFi. At the moment, I can't suggest a better and simpler than this solution.
I'm sure if you have a lot of USB wifi adapters, you also have a couple of old routers.