Thank you for your question.
Actually, the GST (Goods and Services Tax), as you can see by its
name, is a tax on both goods AND services. If you provide services to
a Canadian, you must charge the GST tax of six percent.
Wikipdia entry-- GST
The methods needed to get a tax identification number, or employer
identification number (EIN), in the US are not difficult.
Unfortunately, because you have a foreign address, you will not be
able to apply online but will have to apply through the regular postal
IRS-- EIN application
The form is here: (pdf file)
You will mail it to the very last address on this page:
It should be relatively simple from there.
You do not register with the national government of the US for
businesses; you would register with whatever states you do business
in. If there is one particular state that you do repeat business in,
register in that state. You can find the rules governing incorporation
on that state's website. You would pay tax to that state for income
generated there. You do not need a US bank account to incorporate in
the US, as far as I know.
tax id number application
If you need any additional clarification of my answer before rating,
let me know and I'll be glad to assist you.