What are some good Eastern US native shade flowering plants?

Annuals.

Coleus has so many varieties and although they do bloom, the most fascinating thing about coleus is the colorful leaves 24/7.

Impatiens. Impatiens come in so many colors and need zero dead heading while they bloom nonstop all summer long until the frost or in warmer climates, they bloom longer.

Begonias. Begonias also come in dozens of varieties and colors, while most are constant bloomers with either small single blooms or large double blooms.

The above mentioned plants are annuals which flower continually and are not hard to maintain as they need no dead heading and are super easy to grow.

Google the plants to find your favorites.