In order to get on the floating native village Kahwoka Othunwe, you will have to go the Canada route; it's most easily accessed through San Francisco; simply explore and a Gyrocopter route will open up to Gastown. From there, make your way to Calgary; do NOT go past it!
I have read before that you need to have whiskey in your inventory for things to work from this point on; this did not prove to be true in my experience, as I did not find whiskey during the run I got this on. I had several other conversation opener/bribery items in my inventory, none of which came into play for this, either.

So: In Calgary, Passepartout will be involved in an altrication with some Cree people, during which you will have the chance to nick a "Device" (which will later turn out to be some sort of tracker). This is missable afaik; keep your eyes peeled for a dialogue option along the lines of "I pocketed it" or something.
Explore again and keep talks going for as long as possible.

After all that is done, you need to make your way to Toronto in a missile-type aircraft. This journey will be interjected by a native American woman, who will then take you prisoner and on to Kahwoka Othunwe, under the suspicion of you and Fogg being whiskey smugglers; I assume that this is where the assumption of needing whiskey comes from, but the main "ingredient" here is indeed the tracking device you took off the Cree boy, with or without whiskey.
Once all this has gone down, you will automatically be taken onto Kahwoka Othunwe, at which point the achievement will pop.

...and when they say that, they really mean it; you can't fly over the falls, at least in my experience.

So after you arrive on Kahwoka Othunwe, there will be a trial. You have to be charged guilty in order for things to work out later; if they charge you not guilty, immediately quit the game (don't pick any further dialogue options) and it will start you off at the beginning of the trial again.
When you're charged guilty, Fogg will start developing an escape plan. I chose to stay positive and assertive towards all of his somewhat idiotic ideas - it's very likely that things work out anyway, though.
You will decice to snatch an aircraft; sadly, Passpartout is not able to fly it. Again, to be safe, stay resolute until the last second; you will end up landing in the river flowing down Niagara Falls, which is a railroaded event from this point on - meaning that pretty much once you're charged guilty, you're sure to get the achievement afaik :)

Happy farming!