Let's say after a year of work at current employer, I get a better offer and send papers to register additional employment. Does that add another 3 years I can work in the USA, or it still stays at 2 years?
3 years can only be acquired through extension, only your employer can apply for
The extension. If you get a new TN it will be only for 1 year and you’ll have to renew each year. You can hold up tu 3 TN visas. Each have to be renewed according to your expiration date. Not because your current one lets you stay for 3 years it means that you can work for the new employer for the remaining of your current extension with your current employer. You can work for specific employers based on the specific timeframe mentioned in the different TN visas
3 years can only be acquired through extension, only your employer can apply for The extension. If you get a new TN it will be only for 1 year and you’ll have to renew each year. You can hold up tu 3 TN visas. Each have to be renewed according to your expiration date. Not because your current one lets you stay for 3 years it means that you can work for the new employer for the remaining of your current extension with your current employer. You can work for specific employers based on the specific timeframe mentioned in the different TN visas