OK, technically, the battle for Texas Independence wasn't a US war. Considering the fact that a healthy percentage of the men involved were Americans, maybe it dies qualify. Texicans battled President/Generalissimo Santa Anna's army during the mid-1830s. The Battle for Bexar [San Antonio] in December 1835, the Battle of the Alamo [Mar 6, 1836] and the Battle of San Jacinto [Apr. 1836] led to the formation of the Texas Republic.
Interest in making Texas a state and adding the southwestern territory to the US helped fuel the Mexican War [1845-48].
For records, check Fold3, Daughters of the Republic of Texas, NARA and sites related to the Mexican War and the Texas Rangers.