The old saying of never confuse geographic proximity with cultural proximity was probably never more true than when trying to compare Mexico with its larger neighbour, the United States.
More than a border separates the two countries and although the economic importance of the USA to Mexico cannot be overstated (80% of Mexican exports are bound for the USA), Mexico is a country unique unto itself with a very distinct approach and business outlook.
Just as it is never a good idea to confuse Canadians with people from the USA, it is just as bad to assume Mexicans will be similar to North Americans. (Mexicans are also Americans, as they will point out to you.)
Thus, although the USA has a large influence, both economically and politically, on the development of Mexico it is a very good idea to do some research into the ingredients that make the country so radically different the other two North American countries before trying to do business there.
The biggest influence US business culture has on Mexico is probably in the large number of US multi-nationals who operate in the country and the business processes which follow in their wake. When working in Mexico, it is essential to find out which type of company you will be working with. Are you liaising with the subsidiary of a foreign-owned multi-national or with a locally owned and controlled firm? This will obviously impact on such areas as business structures and decision making — but less so on issues such as team working and communication styles.
It is also probably true to say that the biggest single significant difference in approach to business between Mexico and the USA would be the much greater emphasis placed on the value of personal relationships within the business cycle. Mexico is definitely a country where relationships need to be firmly in place before significant business will follow.