Under the North American Free Trade Agreement (NAFTA) TN NAFTA Professionals, there are two nonimmigrant categories: TN-1 are Canadian professionals, TN-2 are Mexican professionals.
The employer letter, in addition to offering you the position, has to demonstrate that you meet the requirements (your education and experience) of the position, measured against the professional standards and licensure (where appropriate), and the specific knowledge, skills, or experience demanded by the specific position.
In other words, both you and the employer have to prove the requirements have been met and, for that reason, the employer letter should cover all the bases:
- Position being offered
- Requirements of the position (job description)
- Position is a qualifying professions
- You have necessary education and/or alternative credentials (degree, certificates, diploma, professional license)
- You have necessary experience (as demonstrated by your specifics, which it outlines)