Trim fat from tenderloin; cut tenderloin into 1-inch pieces.
Combine chili powder, cumin, and oregano in a large heavy-duty, zip-top plastic bag; add pork. Seal bag, and shake until pork is coated. Coat a large nonstick skillet with cooking spray; add oil. Place over medium-high heat until hot. Add pork and garlic; cook 3 minutes or until browned, stirring often. Add salsa and next 3 ingredients; bring to a boil. Reduce heat, and simmer, uncovered, 10 minutes, stirring occasionally. Stir in green onions and cilantro.
To serve, place 1 tortilla in each of 4 shallow bowls; spoon pork mixture evenly over tortillas. Garnish with lime wedges, if desired.