Can I use my US phone plan in Canada without roaming fees?

It depends entirely on your specific plan. Some premium unlimited plans from major US carriers (like AT&T, Verizon, T-Mobile) include free roaming in Canada and Mexico. However, many standard plans do not and will charge high daily rates or per-MB fees. Always verify the exact terms with your provider before you travel, as 'free' roaming often comes with speed throttles or data caps. An eSIM is often a cheaper and more reliable alternative.