Unfortunately, you cannot delete or reinstall the Apple preinstalled apps.
I just can't figure out why the bottom menu items would be in Spanish. If the keyboard is set to English, the language is set to English, the region is set to the US in the store settings, the region format is set correctly - the last places that you can change the region settings are right in iTunes and the App Store. Have you tried that?
Go the either/both store(s) and tap on the featured tab. In the bottom left corner of those screens, you can access your Apple ID. Tap that and then make that Country/Region change in there - in both stores if you have to.
There is no other place to change the region. This whole thing doesn't make sense to me if everything else is in English and the stores themselves are in English.
Did you buy the iPad in Spain? How did the bottom menus end up appearing in Spanish in the first place? Or is that the great mystery?