US taxes while living in japan, how bad did I F up?

I’ve lived in japan as a student from 2017-2019. Then worked from 2019 to present.
I was talking with another American co-worker who was talking about filing their taxes for the US and my heart sank.

I’ve never done US taxes the entirety of my life in japan. I can specifically remember looking into what taxes I need to do and seeing that I just needed to worry about Japanese taxes.
Now I’m looking into it again and I definitely should have been filing. Now I see that failing to file taxes, even if you didn’t owe anything, leads to fines.
Anyone know how heavy these fines would be? I’m going back to the US in a couple months and am worried about getting random fines dropped on me 🫠

by Afraid_Brick8887