When should I register / copyright my startup company / app?

I finished creating an app and am expecting a good amount of users after I start advertising it. I live in Canada but I have my green card and am eligible to live in the US at any time. I plan on moving to the US within the next few months so I plan on registering the company as a US company. I plan on moving to New Jersey. With that said, at what point do I have to register my company / company name? Is it okay if I launch and advertise the app / website without registering the company and name first? (I'm asking because I am too busy to go all the way to NJ right now just to register the name and business). Or is the company and name registration mandatory before I launch and advertise the app and start getting users? Additional info: I am currently the only worker and the only one creating the app (so I'm assuming it is a sole proprietorship) but after releasing the app and getting more users (in about a month after release) I plan on hiring a few workers.

I live in NJ but plan to incorporate in Delaware (DE) because the laws there are more business-friendly. And because so many US businesses incorporate there the business and legal communities are more familiar with the DE laws. Some investors insist on it. We're planning on growing large and probably taking investment so that makes sense for us.

Here's a bit of reading on it:

http://www.startupcompanylawyer.com/2009/03/03/what-state-should-i-incorporate-in/

If you're not planning on growing to a complex size, taking investment, and want to keep costs low, then incorporating in NJ may make more sense.