That shouldn't break anything.

You ran it as the normal user ($ prompt rather than # prompt), and presumably from within the user's home directory, so all it'll have done is changed the group ownership of all files to root (doesn't matter - as it's a single-user system, the group ownership of the user's files shouldn't affect anything) and granted everyone read (and execute) access to all files (again, not really important on a single user system).

Do you actually see any issues?