According to history.com, different cultures have celebated the spring equinox for different reasons and in different ways. In ancient Maya, Mexico, people publicly gather on the equinox to watch the sun make shadows against the Pyramid of Kukulcan or El Castillo. The shadows are said to resemble a large, moving snake that descends down the pyramid throughout the afternoon as the sun moves.
In the U.S. there is no one-fits-all ritual, per se, that Americans rely on to celebrate the spring equinox. It has become more about enjoying the weather, spending time in nature, planting flowers or gardening, and even decorating Easter eggs.