If you are logged into your iTunes account, local charts are what you should be seeing. Unless your account is set up in a different country.
I don't know of any way to change stores on the iPad, unless you have a second account in that country. Then you could just sign out with one ID and sign back in with the other. You do that at the bottom of the screen.
On the computer you can go to the bottom, there are a bunch of links. Under the Manage column is an option to change country. At least it is there in the US store. I changed it to South Africa on a whim, it signed me out and took me to the store, but there was no link at the bottom for choosing a new country was gone.
Fortunately when I tried to sign in again it told me my ID was only good in the US, and took me back to the US store.