International Loan Interest Rates

I bet I am about to reinvent the wheel with this idea:

Since the mortgage interest rates vary between different countries, why not set up a lending company with offices in many countries, borrow business loans from banks in the country with the lowest current rates and lend this [wire-transferred] money at very competitive rates in the remaining countries (accounting for exchange rates and transfer cost, of course).

I would think this is how it already works, however currently the US loan rates seem to directly depend on the rate set by the Federal Reserve (and not on the lowest current rate in the world, as it would given this idea)

Update: my friend informed me of Carry Traders who apparently operate on similar principles, but within the market framework and borrow specifically short term, while lending long term. My initial idea is to lend mortgages for the same long term as they are borrowed.

Eco5 has useful international interest rate data, and
EconStats has the historical US interest rates

Update #2: I got a second tip regarding the formula which I thought would be cool to put together. Of course it already exists and it is called Interest Rate Parity.