Netherlands AOW Pension taxable?

I'm in the US. My wife (joint return) gets a small monthly payment from the Netherlands AOW pension, which is something like their equivalent of SS. The money is deposited here by an American bank, but there was no 1099. The Netherlands sent their own annual statement, also not a 1099, showing total value in Euros. So I guess my own records of US dollars actually deposited is the only record of this amount. It is income, so I assume it is taxable. I entered it in TaxCut under 1099R, selecting the option of "no 1099". I was surprised to discover taxes increased about double what I expected, both on that taxable income, and also tax on my own received SS increased a similar amount. Does this sound right? This is my first year on SS. I am past full age for my SS. I do have other income to exceed the SS limits.