> There's gum stuck to the back of my shoe.

The back of the shoe is the opposite of the front of the shoe, not the opposite of the top of the shoe. More likely (since the bottom of the shoe would pick up any gum on the ground):

There's gum stuck to the bottom of my shoe.
There's gum stuck to the sole of my shoe.

The Russian indicates this meaning.

The Japanese would also still match. 裏 could refer to bottom or back.

Interesting. Thanks. I unlinked the Russian from this sentence and added a new translation.

I misspoke

I meant it would still match the Japanese if the change to "sole of shoe/bottom of shoe" was made
裏 could literally refer to bottom or back, and I'd imagine here it refers to bottom
That fix means it would also probably match with the French I think (it literally says "heel", at least that's how I translated it into Spanish)
I can't speak for the other languages

I am not sure if this would invalidate any of the other translations, but 'bottom' definitely fits the Japanese better so I have changed it.

Duplicates of this sentence have been deleted:
x #10568220

French says heel, so it kinda refers to the bottom?
Russian might be OK since it's linked by someone else to an identical sentence
The other languages I don't know

I would prefer to see the French linked to a more specific English translation.