Has Mexico always been considered to be in North America?

No, not always. Although Mexico is now widely regarded as part of North America, this has not always been the case. Historically, Mexico was often considered part of Central America, and some scholars still include it in that region today. The division between North America and Central America has been variously drawn at the Isthmus of Tehuantepec, the Mexico–United States border, or the Panama Canal.

In the 19th century, the term "North America" was often used to refer to the United States and Canada, while "Central America" was used to refer to the countries south of Mexico. This distinction was based on political and cultural factors, as well as geography. The United States and Canada were seen as having more in common with each other than with Mexico and the other countries of Central America.

However, over time, the definition of North America has expanded to include Mexico. This is due in part to the increasing economic and political ties between Mexico and the United States. Mexico is now the United States' third-largest trading partner, and millions of Mexicans live in the United States. Additionally, Mexico has become more integrated into the North American Free Trade Agreement (NAFTA), which also includes the United States and Canada.

As a result of these changes, Mexico is now generally considered to be part of North America. This is reflected in the fact that the United Nations and other international organizations include Mexico in the North America region. Additionally, most maps of North America now include Mexico.