Will's, estate, or QTIP?

I'm a US citizen that has several accounts in the US but I live overseas. My wife is a non US citizen and in the event of my death I would want her to be able to get these funds. A couple of the accounts have said they can't give the money to her as she's not a US citizen and she doesn't have power of attorney. Is a will good enough for her to show to access these funds? I've heard of a QTIP, but reading up on them they're more for distributing funds on a time basis not a one time payout. What's the best way forward in order for my wife to get these funds all at once to a foreign bank?