Unfortunately it is not possible to delete your teams in Premier League or La Liga.
Each Facebook profile is only allowed one team. You can change out the roster, but it is not possible to completely remove the team.
However, you can remove the app from your profile, which serves the same purpose.
To do so, you need to access the 'Privacy Settings' for your profile.
Privacy Settings > Ads, Apps, and Websites > Apps you use .
There will be an 'x' next to each app you can use to remove any app from your profile. I hope this helps!