Dual citizen on temp business assignment to U.S.

I am a dual citizen (Canadian/U.S.). I have never lived or worked in the U.S. but I have a U.S. valid passport and SSN. I have been offered a temporary work assignment at our NYC office for 6 months. I would continued to be paid by my employer in Toronto in Canadian dollars, deposited into my Canadian banking account. I will however need to rent a place during my stay in NYC, but will be maintaining my residence in Toronto, to which I will return after my 6 months are complete.
Do I need any further documentation other than my U.S. passport and SSN to work in the U.S.? I am concerned immigration will not be satisfied as I have never resided in the U.S. nor used my American passport. Also, what about my return to Canada? Will Canadian customs question why I have lived outside the country for 6 months?
Any other issues I should be aware of? Taxes? Canadian healthcare?
Also, any advice on opening up a bank account in the U.S.? How will I be able to pay my rent if my pay is only deposited into my Canadian account?
Thanks kindly for your help all, much appreciated!

you are free to do what you wish in US and canada, leaving and returning as you wish.

As a US citizen you have been filing a US tax return every year (right?), so the source of the income is not that crucila (except that you will not be able to claim foreign income exclusion).
All other matters are easily handled.

For more tax info see my signature.

While I realize that I should have techinically been filing a tax return in the U.S., it was my understanding that my income was too low to be worth the trouble. I hope this decision won't come back to haunt me. Obviously, going forward, I will.

If you are single, unless your income was less that ~$10K each year, then you absolutely needed to file.

There is a difference between filing and owing tax. You can't say you don't owe tax until you file and apply all the credits, and deductions you are entiltled to.

Also, not reporting the existence of any RRSPs is a huge penalty all by itself.

This is not the same standard that CRA applies, which is simply you don't need to file unless you owe tax, or need to report some tax event.

Your first US return will trigger an investigation
see signature for more info

If you are working in the USA, your first tax liability is to the US regardless of whether your employer is Canadian or not. If its just a week or two you can pay later and not worry but if you are there for 6 months and your employer just deducts the Canadian tax, you can find yourself with big US tax bills (federal income tax, state + NYC income taxes & possibly FICA) next April with interest and penalties building because US tax was not paid through the employment period. Better to be paid out of the NYC office while you are there with W2s issued not T4s.

It is not quite true that US would have first crack -- Cdb resident self-employed would be an example. That's why there are treaties.

Best leave this question for experts at forum below.

My understanding (as a US/Canadian dual citizen) is that the treaties do not apply if you are a US citizen.