what would happen to the relationship of canada and united states if quebec separates?

Very little.

We'd send a new ambassador, who speaks French.

what might happen to their trading system? :O

I'm sure the U.S. would quickly establish trading agreements with Quebec.

I was thinking about that too but I wasn't sure. thanks :)

"It ain't gonna happen"

In the last few years, many Quebecois have realized that they will have to give up their universal health care and their Canada Pension, so they are not going anywhere.

Thanks, Reiny, for the perspective of a Candian.