Here is how it works (hopefully my explanation won't make you more confused!):
If you're self-employed or run a business in Canada, you (and your spouse) have got until June 15 in Canada to file (instead of April 30). US taxpayers residing abroad automatically get an filing extension of two months, so American residents of Canada have a US deadline of June 15, too (instead of April 15). Tax payment deadlines remain in April, even if filing deadlines are in June (so you have to estimate your taxes owed and make a payment based on the estimate). For residents of foreign countries, US taxes are usually easy until you earn more than a certain amount (in 2014 it will be $99,200 per taxpayer, in US dollars). For most people with just employment income you can file form 2555 with your 1040 and you won't owe anything in the US. After that amount, the calculations get harder and you can theoretically wind up owing the US if your tax in Canada was lower than your tax in the US, and even if it wasn't, you have to file in the US anyhow, which means you have to figure your foreign tax credits to get your US tax liability to zero if your income was above the threshold. If you have income from sources in the US and in Canada, or you run a business, or you changed your country of residence in the past year, it can get much more complicated. But for the average US taxpayer living in Canada and making 100k Canadian a year (each US taxpayer spouse gets the exclusion, but your Canadian spouse who is not a US taxpayer doesn't have a US filing obligation) only from Canadian sources, it's not going to be hard (just irritating...).
Also, if you've got accounts outside the US with more than $10k in them at any point in the year, you've got asset disclosure forms to file (FBAR and/or FATCA). Those are really stupid, but the penalties for failure to file them are stiff...