The number and distribution of spots helps to identify the species of ladybug. These are in a large family of beetles called coccinellids (Coccinellidae), and there are MANY coccinellid species in North America. Many species are marked with spots or bands. With few exceptions, both larvae and adults are beneficial as predators on aphids and other pests, often resulting in effective control of these plant pests. A few species are phytophagous and are crop pests.
I can't speak to how lucky they are, but the deliberate introduction of a non-native Asian ladybug has driven at least a couple of our native Ladybug (e.g., two-spotted ladybug) numbers down dramatically. Nobody has really noticed, because we just think of a ladybug as a ladybug.