The TN visa, created under NAFTA and continued through USMCA, lets qualified Canadian and Mexican citizens work in the U.S. in specific professional categories. The initial stay is up to three years with effectively unlimited extensions. The E-1 Treaty Trader visa is for nationals of treaty countries engaged in substantial trade principally between the U.S. and their home country. The E-2 Treaty Investor visa is for nationals of treaty countries making a substantial, at-risk investment in a real and operating U.S. business.
TN status can often be obtained at the port of entry for Canadian citizens, or through consular processing or a USCIS filing depending on your circumstances. E-1/E-2 registrations typically require consular processing or, for those already in the U.S. in another status, a change-of-status filing with USCIS may be possible.