The original Famicom does work on a US TV. It's just that the channel settings of the original correspond to different channels than you're used to when using a US TV. You have to set the TV to channel 96 or something. Now, why channel 96? I don't know...

Oh, and on some US TV, I think the AUX or whatever setting works for original. I have an AV Famicom but never tried it. From what I've heard, it works fine, like an AV NES.

It is probably just a conversion thing.  Try it on 96 and see if it it works.

While both Japan and the US use ntsc, the frequencies for the channels are different which affects rf video but not RCA.

The jp channels 1 and 2 are frequencies which are commonly in the 90-100 range on most TV's. Most commonly, they're 95 and 96. If you're  having trouble, try 90-100 on both the 1&2 setting on back of the famicom. If it still doesn't work, try a different TV. If it still doesn't work, send the famicom to me as a birthday present!