Commelina communis tends to have petals that are less rounded and a tad pointed on the end. They are also held in a very upright position. The petals here are more rounded and held more to the sides which is why I would choose Commelina erecta over C. communis for an ID. The form and position of the stamens, staminoids and pistil look more like C. erecta, too. However, there are quite a few species in the USA that look similar so I'm not swearing to anything.
