Heat a large pot with water. Place chicken thighs inside water and boil until you see a brownish foam ~7-10 minutes. Discard foam from the top. Add in carrots, celery, and onion and turn fire to medium low.
While vegetables are cooking, prepare meatballs. Place ground beef, shallots, garlic, garlic salt, seasoned salt, red pepper flake, pepper, green onion, egg, and chipotle powder into a large mixing bowl. Use hands to mix together all ingredients for meatballs. Knead meatballs for 1 minute, lifting the meat mixture and using force to toss it back into the mixing bowl. Repeat at least 5 times until mixture begins to stick together. Set aside.
Check broth. Remove chicken thighs from stew and place aside for another dish. Add in Mexican squash and crushed tomatoes. Add in seasonings as well: bay leaves, garlic salt, and seasoned salt.
Begin forming meat mixture into meatballs 2 inches in diameter. After all meatballs have been formed, drop meatballs into the soup and allow to cook until their color turns from pink to light brown ~10-15 minutes.
Spoon into individual bowls and garnish with chopped cilantro and a squeeze of lime juice if desired.