To answer this question we draw an analogy to medicine - if you have a toothache and a foot problem, do you look for a dentist who is also a podiatrist or do you talk to two separate specialists? The same works for taxes. As long as your US tax specialist is well versed in expat returns - they will certainly know everything about your local country issues and how they should be integrated in your US tax return. 

Let's look at the UK as an example. While you can probably find one or two firms that specialize in dual-filing of UK&US taxes, the fees they charge will likely border between obscene and ridiculous. The reason is simple - while there are thousands of Americans in the UK who need to file taxes in both countries, the number of competent tax preparers who can do both is minuscule. And (their marketing spiel notwithstanding) truth be told, there is nothing special about UK (or any other foreign country) as far as IRS is concerned. All taxes paid abroad are counted the same whether they were paid in the UK or Ukraine. The same works for National Insurance, ISA contributions, QROPS, council tax or anything else that you think is unique to the UK - it is not. 

The only real upside from hiring one accountant to deal with both tax systems is reduced communication. However - do you want to pay three or four times for the same service just to have to deal with one professional instead of two? This is certainly a personal decision - but make the determination knowing exactly why you make the choice.

1. Expertise. By working with us you will avail yourself of the top expert in the field of US expatriate taxation (see http://www.taxesforexpats.com/about/why-hire.html).  We exclusively focus on American expats and, therefore, deal with all kinds of situations that regular accountants (even those working abroad) may see rarely or never. Your local accountant is simply unlikely to possess the same level of expertise. While they may be knowledgeable in tax issues pertaining to the country you're living, ultimately what matters is how versed they are in US Taxes and how much they deal with the IRS. There are simply no accountants outside the US who can match us on this count.
2. Cost If you live in a high-cost location (such as most of EU, Switzerland, Singapore or Australia), local accountants will charge fees that exceed ours by a factor of 2-3 (and then add a 20% VAT on top). On the other hand, if you live in a developing country (ie the rest of the world) - there simply aren't any knowledgeable local accountants that you can approach for US tax help.
   
3. "Visiting the Office". Reason most often cited when looking for a local accountant is the 'ability to stop by the office'. But let's consider it. Your first visit will likely take roughly 2-3 hours (unless you share the same office building). Thereafter - will you visit your accountant every time you need to ask a question, or will you use email / phone instead? Most likely you will email or call for years to come. However, once you are communicating by email, it is irrelevant where the office is located - it takes as long to for an email to reach NYC as it does to travel next door. 
4. Trust. You probably want to meet your accountant so that you can assess how trustworthy, competent and knowledgeable he or she appears. But let's face it - what qualification do you possess to gauge whether he really knows the tax law, how promptly he will answer your questions and how much attention your case will receive? Will you ask to see their CPA exam scores?
   

So at the end of the day - you have to decide whether the privilege of meeting your accountant once in a nice office justifies paying triple + VAT for years to come.

So, at the end of the day, the concept of prevention from double taxation holds true, but the results are stretched over time.

Working as a Canadian government employee for the local government does not make you exempt from the U.S. taxation.

Paragraph 149 (1) of the Canadian Income Tax Act exempts from tax, on a reciprocal basis, U.S. citizens paid by the United States for services rendered in discharge of government functions in Canada. Similarly, United States would not tax Canadian citizens receiving remuneration from the Canadian Government for services rendered in the discharge of government functions in the United States. 

• Government-guaranteed compulsory superannuation funds do not need to be reported.
• Voluntary savings through self-managed superannuation funds must be reported.