As an American living abroad, it has been interesting (and depressing) to watch the slide of the USD. When I arrived in Oz, 1 AUD was worth .74 USD. Today it is worth .94.
That is depressing in an obvious sense, it isn't all rain clouds. As the USD declines, import of American goods becomes more attractive to foreign markets since, in a sense, the American goods are "discounted". A product at USD 100 would have been AUD 135, but is now AUD 106. Indeed, you see this both in markets introducing new American lines, but also in the average consumer who is more willing to buy American goods online. Additionally, the US becomes more attractive to tourists since their AUD, CAD, Euro, L, can go further than they would have before.
In a very long term sense, it is bad, especially if the currency of note becomes the Euro. I seriously doubt a North American currency would do much to help us, either, since the US and Canadian currencies are at near parity (and no real place to go but down), and the peso isn't exactly an economic powerhouse.
Only strong economic stewardship is going to help the currency, and continually slashing interest rates isn't helping, especially as the Commonwealth nations are raising their rates to high levels. More grassroots programs are needed to infuse wealth at the bottom to entice individuals to take loans. If you have no money, it doesn't matter if rates are 5% or 2.5% ... you can't borrow anyhow. I think that's been the Fed's (and the Bush admin's) problem in dealing with his whole issue. Cutting away at interest rates isn't doing anything but sending currency investors running to their nearest Euro or Commonwealth currency.