Okay, since I work in Detroit and currently a Canadian PR in windsor....
The bottom line is, if you are a citizen, you can work in US with TN visa which you can apply at the entry of US without appointment and renew it every year.
And if you are not a citizen, no matter wherever else you come from, you will have to have "working permit" to work in US.
A working permit typically indicates, but not limit to, H1B visa. (otherwise it could be J visa or free trade visa)
To apply H1B visa, you have to have a US company to sponsor you with the reports, documents, and etc.
Most of the mid-size or small company don't like to do this coz they are not comfortable to
disclose their financial and funds status clearly.