Preheat the oven to 375 degrees F. Toss the tortilla strips with 1 tablespoon vegetable oil on a baking sheet, spread in a single layer and bake until crisp and golden, 12 to 15 minutes. Season with salt and set aside. Meanwhile, heat the remaining 1 tablespoon vegetable oil in a large pot over medium-high heat. Add the chorizo and cumin and cook, breaking up the meat with a wooden spoon, until browned, about 4 minutes. Add the sweet potato, chicken broth, tomatoes and 1 cup water and bring to a boil. Reduce the heat to maintain a simmer and cook until the sweet potato is tender, 10 to 15 minutes. Stir in the spinach and lime juice and season with salt. Divide among bowls and top with the tortilla strips, cilantro and avocado.