I think the difference is very subtle. Both of them mean "to concentrate", but "be focused" is more reflexive, as if "focus" was the action itself, but "be focused" was rather the state of mind, if that makes sense to you.
- I need to focus on my speaking skills right now
- I am focused on my speaking skills right now
I believe native speakers would use both, it's just a matter of structure.
I hope that helped!