In a second round singles match, the lucky loser Indian suffered a 4-6 6-2 4-6 loss to the local wild card, ranked 60 in the world.
It was second consecutive defeat for Ramkumar against the American, having lost to him in the second round of the Roland Garros Qualifier in 2015.
After Ramkumar's defeat, India's interest in the tournament remains in doubles with Rohan Bopanna set to play his second round match with partner Ivan Dodig.
They face the team of Colombia's Juan Sebastian Cabal and Italian Fabio Fognini, who both are top-25 singles players.