RE:US stocks to a Canadian exchange - ???Should be no problem if you're dealing through a normal broker. I do it once in a while but you'll get skinned on the exchange rate - typically > 1% each way depending on how big the transaction is. For instance, if you buy $1000 worth of an interlisted stock in the US through a Canadian funds account you'll be nailed with a $15 currency exchange charge in addition to brokerage.
If you have both a US funds account and a Canadian funds account and you want the interlisted stock you bought in the US account in your Canadian account you can get your broker to journal your stock overnight from one account to the other so that you avoid the exchange charge but the eventual proceeds are in the currency of the account you sell your stock through. This only works if you had enough in the US account to cover the purchase so that whoever sold you the stock gets paid in full in US funds - otherwise you still get nailed for the exchange rate on the balance.