Below is a chart of Rev. Rul. 63-252, which was cited in an I.R.S. determination letter that was released recently. In the revenue ruling, the I.R.S. provided five different examples where contributions were made to a U.S. charity and ultimately sent to a foreign charity. The I.R.S. held that in three of the scenarios, the donor was not allowed to deduct the contribution. In two of the scenarios, the donor was allowed to deduct the contribution under Code §170.
The chart can be viewed as a PDF file here: Rev. Rul. 63-252