The Sounders went ahead midway through the first half through Kenny Cooper, but their hopes of securing the three points hit a snag when Djimi Traore was sent off just before the hour mark. Federico Higuain levelled from the spot immediately afterwards before Meram's last-gasp effort gave Columbus their third win from three matches.
They sit top of the embryonic Eastern Conference standings by two points ahead of Sporting Kansas City, who also came from a goal down to claim a 3-2 win at ten-man Colorado in a game where all five goals were scored in the final 40 minutes.
Graham Zusi opened the scoring just after half-time and although two penalties from Vicente Sanchez put the Rapids in the driving seat, they were reduced to ten men after Benny Feilhaber had levelled when Marvell Wynne was sent off. Kansas took full advantage as Dom Dwyer scored the winner.
Mauro Diaz's 84th-minute winner helped unbeaten FC Dallas to a 2-1 win over the Portland Timbers, with both sides playing most of the match with ten men. Dallas midfielder JeVaughn Watson and Portland defender Michael Harrington were both sent off just before the interval, before the hosts took the lead on the stroke of half-time through Blas Perez.
Portland levelled through Matt Hedges' 66th-minute own goal, but it proved to be in vain as Diaz struck late on to give Dallas their third win in four games.
Real Salt Lake also maintained their unbeaten start to the season, with two goals from Alvaro Saborio, the first from the penalty spot, either side of Luis Gil's strike helping them to a 3-0 win over Toronto FC. DC United earned their first point of the season in a 2-2 draw at home to the Chicago Fire, who are also yet to win this campaign.
Jhon Hurtado put the visitors ahead and although goals from Fabian Espindola and Perry Kitchen turned the match on its head, both sides settled for a point when Quincy Amarikwa struck eight minutes from time for Chicago.
Montreal grab first point
Montreal Impact also claimed their first point as they earned a 1-1 draw at Philadelphia Union despite being reduced to ten men. Philadelphia appeared on course for all three points when Vincent Nogueira's goal was followed by Andrew Wenger's dismissal, but Montreal would not roll over and Marco Di Vaio ensured a draw 10 minutes from time.
The Vancouver Whitecaps and New England Revolution were both 2-1 winners in their respective matches. Jordan Harvey's strike and Kenny Miller's penalty sealed victory for the Whitecaps over Houston Dynamo, whose goal came from Ricardo Clark.
Meanwhile, Lee Nguyen's last-gasp strike inspired the Revolution, who took the lead against the San Jose Earthquakes through Victor Bernardez's own goal before being pegged back by Chris Wondolowski.