You can turn almost anything into 3/4 if you try hard enough: can't say I always like the results! Various ceilidh band "waltzes" which were originally in 4/4 include Loch Lomond, A Man's a Man for a' That, My Love is Like a Red Red Rose - yuk!
I would think of House of the Rising Sun as being in 6/8, not 3/4. (Based on The Animals' version which most of us in the UK would know). It's more of a picked out arpeggio: 12and3 456, 12and3 456, etc rather than a strum.
And I certainly wouldn't "strum" on some of the others mentioned: a little simple fingerpicking up and down the strings would sound so much nicer on Amazing Grace, for example.