At the National Archives, in Record Group 94, there is an "Index to Compiled Service Records of Volunteer Soldiers Who Served During the Mexican War."
M616, 41 Rolls in alphabetical order.

Unfortunately, there are no rolls containing the Compiled Service Records for Louisiana units. That is, as of the microfilm index dated 1998 which I possess.

States covered are: Mississippi, Pennsylvania, Tennessee, Texas and Mormon Organizations.