If Canada found itself in a situation where it was no longer competitive with the US we would need to take action to solve this problem. “No longer competitive” means that someone could get the same products made elsewhere for cheaper or more efficiently. They could hire workers in the US for the same or lower amount of money and get their goods produced. Any goods that are produced in this uncompetitive version of Canada are done so at high cost and so must be resold at higher cost. This is obviously not good.
As discussed previously Canada has a floating exchange rate. So if this situation arose one possible solution would be to devalue our currency. This means getting more Canadian dollars on the market so that they are worth less. This means that the average Canadian worker does not see a change in the amount of money that appears on their paycheck(nominal wage) but the value of that money is actually less(real wage). So as the real value of Canadian dollars gets lower, Canadian goods become cheaper and people buy our stuff.
With a fixed currency like the Euro this is not an option. Greece cannot devalue its currency because it does not control it. So as Greece tries to recover from its problems it must find a way to become competitive in the Euro and world markets. They need to grow their GDP but they have no way to reduce the real wages in the country. This of course means that they are going to have to reduce real and nominal wages. This means that people have to take actual pay cuts. As you can imagine it is alot easier for a government to devalue a currency than to tell people they are all taking a pay cut. People are not too happy about it, obviously.
I am sure there will be much more to say. The EU has recently decided to setup a massive a financial safety net, I have not read all the details so that will maybe be discussed in the future.