Ok y'all! Here is your promised native substitue for Rose of Sharon: Haberdleaf rose mallow (Hibiscus laevis). This guy is native to Central and Eastern North America and is a perennial rather than a shrub. Here in SC PA it is a caterpillar host plant for at least 26 species of moths and butterflies.
Growing up to 6' tall and 3' wide, the rose mallow prefers rich soil and full sun. It is often found growing wild along streams and swampy areas, making it a good option for a wet spot or a rain garden. It blooms with 6" wide white to pink flowers in mid-summer.
Most rose mallows you find in the garden center are cultivars or hybrids. Be sure to ask for this straight species native for maximum ecological benefit. Especially avoid those hybrids whose leaves are not even green! Go ahead, ask me why.
Sources: USDA, Missouri Botanical Garden, National Wildlife Federation