IMO, the next single should be "Up All Night". It's a catchy, uptempo, fun song. They can do a cheap video while on tour in the US ... maybe use some footage from the concerts, backstage and films some additional scenes.
If not that one, "Tell Me a Lie" would be a good candidate. Also uptempo and has some character.
I guess I prefer the uptempo songs. "Gotta Be You" didn't do well, I would rather not risk it again. Ballads should be kept as album tracks (unless the song is really amazing).
But if they plan to release another album this year, they might not release more singles ... I don't know. I would release at least one more in the UK and I wouldn't bother releasing "Gotta Be You" in the US and around the world.