Assuming you're a US citizen/tax resident filing a form 1040, it is. Unless your country has a tax treaty with the US to say otherwise.
Most countries that do have a tax treaty with the US, have a special clause that discusses this type of income, however not every country has a tax treaty with the US (most don't, in fact), and not every country that does extends this provision on US citizens (most do).
Specifically to Israel: Bituah Leumi (Social Security) payments are exempt under the Israeli-US tax treaty. You're receiving it from Israel, and for the purposes of the US tax law - you're a resident of the US, thus you qualify under article 21. In fact, the treaty says that neither country will tax that, so you should check with the Bituah Leumi office about this (maternity payment is otherwise taxable income in Israel).