I want to dance square dance on the computer, then put it on a USB flash drive and watch it on TV. How? Solve it.

It depends on your TV supporting USB.

Today's TV sometimes deceives people,

Some TVs support USB flash drives, but only JPEG, GIF and picture formats.

When buying a TV, you should pay attention to buying a TV that supports playing videos.

If your TV doesn't support it, there is no need to change it. Buy a DVD, then burn the square dance into a CD, and you can watch it on TV, and it doesn't cost much.