Aha, over six years later I'm posting this.

It's certainly not a Dutch folk song. The Smothers Brothers often took certain songs and sang them as something different. The Israeli song 'Tzena' became the song of the Uruguayan camel races, 'Hava Nagila' was the Venezuelan rain dance, 'Whiskey in the Jar' was sung as an Eskimo folk song, etc.

And the spelling 'Maria' is correct, even though there probably aren't that many people (in America at least) who pronounce it that way anymore.