It's positive, say Benjamin James Waddell and Matías Fontenla, who studied what happened when natives of Guanajuato returned to Mexico from the United States. According to J. Wesley Judd of Pacific Standard they brought back human capital acquired in the United States and enriched their neighbors.
The Mexican Dream? The effect of return migrants on hometown development
...when former migrants come back to their hometowns, "fewer infants die before the age of 5, more children attend school, literacy rates improve, per capita income rises, and citizens engage in electoral politics in greater numbers," ....Which raises an interesting contrast in inequality between Mexico and the USA.