Since the 70's, there has been a populous of immigrants to North America,
from countries where Salsa dancing was popular - Cuba, Puerto Rico, Colombia -
dancing Salsa in the Latin Nightclubs they frequented to get their weekly taste of home.
Their salsa dancing was quite different from what we see in nightclubs today.
With Salsa's growing popularity, more and more non-Latin people began dancing it and teachers from North America ballroom studios began to tap into its popularity. They taught it by integrating steps from the "Ballroom" version of Mambo dance (not the Cuban dance version) - the version that the Arthur Murray dance school franchise had made popular in the 50's. In New York, where the Arthur Murray dance franchise started, the words Salsa and Mambo today are used interchangeably. This mambo style salsa became significantly popular outside of Latin America.
In recent years Salsa's popularity has increased to world-wide proportions. It is being danced all over Europe, Asia, North America and now even the Latin American countries that have not traditionally danced Salsa such as Argentina and Mexico, have thriving Salsa scenes.