Forming a Corp in US being Canadian citizen
The only restriction for non-U.S. citizens is that you cannot start a so-called S-corporation in the U.S. However, you can start a C-corporation or a Limited Liability Company in the U.S. without a problem. You can read our article about the differences between S-corporation, C-corporation and LLC for more information on these types of entities.
So, you can can as many U.S. entities as you'd like and they can be either limited liability companies or C-corporations. They can also be formed in any state that you with, including one of the incorporation havens: Delaware, Nevada and Wyoming.
You can also structure the ownership of your companies in any way you want. Both the LLC and the C-corporation can be owned either by you individually, by another U.S. LLC or corporation or by a foreign company - and even by a combination of these options. This gives you a lot of flexibility.
Finally, to your question of working for one of your companies. You need a visa to be "employed" by one of your U.S. companies and receive a salary in the U.S., but nothing should stop you from working for your companies for free and just collecting the profits. Naturally you (and in the case of C-corporation, also your company) would have to pay taxes in the U.S. To pay taxes, the company will have to obtain a Federal Employer Identification Number (EIN), which is a very simple process, and you would have to get an Individual Taxpayer ID number (an ITIN). Just be aware of that.