There is no special immigration path for US citizens. She will need to qualify and apply through an economic immigration program just like anyone else. Her odds will depend on a number of factors such as years of work experience, how many points she can score, etc. Express Entry is one option for immigrating. She will want to score 470+ points to have a decent chances of being selected. I would recommend she start by researching the Express Entry program in detail so that she will know what's involved: https://www.canada.ca/en/immigration-refugees-citizenship/services/immigrate-canada/express-entry/works.html
A job offer is generally not enough to get a work permit. Generally speaking an employer must also obtain an approved LMIA. It can be very difficult to find employers willing to go through this process.
If you get married, there may be additional options available.
There is no special immigration path for US citizens. She will need to qualify and apply through an economic immigration program just like anyone else. Her odds will depend on a number of factors such as years of work experience, how many points she can score, etc. Express Entry is one option for immigrating. She will want to score 470+ points to have a decent chances of being selected. I would recommend she start by researching the Express Entry program in detail so that she will know what's involved: https://www.canada.ca/en/immigration-refugees-citizenship/services/immigrate-canada/express-entry/works.html
A job offer is generally not enough to get a work permit. Generally speaking an employer must also obtain an approved LMIA. It can be very difficult to find employers willing to go through this process.
If you get married, there may be additional options available.
There are only a select few NOCs for professionals that are included for exemption. If your girlfriend has experience (education and work) within the NOC then it is possible. She would need a job offer.
Look at CUSMA. NAFTA no longer exists. Whether she can benefit under CUSMA will depend on her occupation. Not all occupations qualify. She will need to secure a job offer in Canada.