The point about the employer being responsible for underwithholding is only a technical point.  See §31.3403-1.  The IRS will first try to recover the shortfall from the individual taxpayer.

The stock doesn't have to be traded on the US markets.  Canadian markets are recognized for tax purposes as well.

You may like to read up on ESOP, which is not the same as ESPP and is governed by different code sections.  Don't see how there would be any "basis" and am not convinced, given the limited info you provided, that the distribution should be reported on Sch D.