Ok so I have an account that is from the US but im from the UK, my question is: Can I buy MSP with my debit card for that account even though im from the UK??
Nope. You're not able to purchase Microsoft Points off of your Xbox with a foreign[sup]1[/sup] credit card. If you're looking to purchase some, you'll have to buy American Microsoft Points off of the internet.
[sup]1[/sup] Foreign to the account's country. So your UK Debit card would be a foreign card on an American account.