I'm assuming having the possibility of another sovereign nation bordering us would be a cause of interest to mainstream America.
Some memos from the US State department which shed light on the US take on a hypothetical "Yes" vote in Québec have been released by the Clinton Presidential Library & Museum, but I cannot seem to be able to link to the originals at the moment.
For one thing, the US position was that this was a matter on internal politics within Canada, and that there would be no rush to recognize a sovereign Québec as the various parties involved sorted out the implications and worked out a new constitutional order in the event of a “yes” vote. Essentially, they were hedging their bets and keeping their options open, including the possibility that a “yes” vote might trigger some sort of negotiated settlement leading to some kind of arrangement between Québec and the rest of Canada. This position was reflected in a speech made by president Clinton.
On the other hand, the State Department also mentionned concerns about the implications on the North American Free Trade Agreement, and saw a Quebec declaration of sovereignty as an opportunity to renegotiate NAFTA, presumably in view of reshaping the terms of the agreement so they would be more advantageous to the US.
See also:
Outside of the official policy of the White House, however, there was a wide view of opinions ranging from a business as usual stance to expressions of concern. You might want to have a look into the special issue of the American review of canadian studies devoted to various aspects and implications of a sovereign Québec. That being said, I haven't noticed our referendum was a subject of concern, or that it even was on the radar, of most of our southern neighbours.