I am a Canadian citizen working for a US company on an H1B visa that expires in October (long complicated story). My company has just restarted my PERM process (Prevailing wage and recruitment care complete). Our lawyer wants me to return to Canada and switch to a TN visa before filing the PERM. My question is can I get a TN after an H1B while working for the same employer? How do I get a "job offer" letter from a company that I already work for?