88 Ford festiva unevenly worn rear passenger tire

The rear passenger side tire was completely bald on the inside only (outside of tire was fine) when I got the car. Put on a new tire and within a month it’s bald again. I don’t think you can align the rear tires on this car so does this mean my rear axle is bent or is it something else? The axle doesn’t look noticeably bent and there is no sign on the car body of something that would have bent the axle. Anyone have any experience with these tiny little 12 tires?

Both front drivers (a Chevrolet and a Dodge) that I had a reason to check the rear wheel alignment, had provision for adjusting the rear wheel alignment with shims behind the stub axle. I would be amazed if your car had no provision for rear wheel alignment.

Wear on the inner edge of the tire means too much negative camber.
Eyeballing it may mean nothing as a suspension component can be bent badly enough to cause problems and not be visually noticeable.
One good pothole could do it.
Sometimes design factors in once the car is aged and the suspension settles.

If you have a small carpenters level try parking the car on level concrete. Place the level vertically against the steel wheel (NOT the tire) and note if the top of the wheel is canted inward.
If you do this you may need a couple of identically thick spacers to shim the level out from the wheel enough to clear the tire. Spacers could be a couple of thick nuts or blocks of some sort.

It sounds like this car was in an accident and the frame is bent - and the only fix for it is to bend the frame back.