Changing keyboard type does not work

Hello everyone!

I just bought a USB keyboard, which has English layout. My Mac built-in keyboard has an Italian layout instead. When I first connected the USB keyboard the keyboard setup assistant popped up on its own and I could setup the keyboard type. The USB keyboard worked for a while, but the day after, when I plugged in my USB keyboard again, it retained the Italian layout, which is pretty inconvenient for me right now. I tried the following:

1. I opened the System Preferences --> Keyboard --> Modify keyboard layout. After pressing the two requested keys to recognize the layout, the system correctly recognized that this is a keyboard with ANSI layout, but then it keeps retaining the Italian layout for some weird reason. This is so frustrating.
2. I tried deleting the file /Library/Preferences/com.apple.keyboardtype.plist, emptying the trash, disconnecting my USB keyboard, rebooting, and reconnecting the USB keyboard again. After setting the layout type to ANSI the keyboard would still not work as supposed and would still be set to the Italian layout.

What am I supposed to do? Any idea? Any help would be greatly appreciated! Thank you!