My wife also worked on the economy during our OUTCAN posting (however, not in the US). In our case, mostly because we maintained our house in Canada, she was considered a deemed resident of Canada. I don't believe a deemed resident has to necessarily maintain a house in Canada, but he/she must maintain a link of some sort (i.e. show a residential tie).
The tax implications can be interesting. In our case, my wife had to meet all the tax requirements in our country of residence (fill out the forms, pay taxes based on her salary, etc). That was all pretty straight forward. The foreign country's tax system is actually simpler than Canada's. However, she also had to declare all of her foreign income (as well as her Canadian income - half the rent on our house) on her Canadian tax return. However, all the foreign taxes she paid were then applied as a tax credit. The big point here is that she didn't get taxed twice. Although she had to declare her foreign income on her Canadian tax return, her foreign taxes were also deducted from it. In our case, mostly because we have the rental income and expenses in Canada, we engaged an accountant to sort through all of this for us. It just made life simpler and in my mind was well worth the cost (which is tax deductible by the way).
On a side note, if you keep your house in Canada and rent it out (i.e. use it as an income property), you should ensure that you declare it as your "principle residence" (involves a letter to CRA - my accountant took care of that). You can maintain a house you're not living in as your principle residence for up to four years (even if it's rented out). If you don't do this and you end up selling the house at a later date, you will have to pay taxes on any capital gain incurred while it was rented. Something worth looking into.