MLS has long been rumored to be exploring the possibility of utilizing instant replay. While goal-line technology isn't quite as expansive as the project MLS has been rumored to be exploring, we will at least get a glimpse of that during Copa America Centenario.
Hawk-Eye Goal Line Technology is the same system that was used in the 2014 World Cup and 2015 Women's World Cup as well as in the English Premier League, Bundesliga, Serie A and UEFA competitions. The system utilizes seven cameras on each goal that track the ball and notify the referee within 1 second of the ball crossing the line. Although its usefulness is limited to the handful of times when a ball is close to crossing the goal-line, it at least provides certainty to the most important decisions.
Although CenturyLink Field will be one of three MLS stadiums to have the system installed for the tournament, chances are we won't see it used in MLS games anytime soon. That would require all 20 stadiums being outfitted with the technology. Back in 2013, MLS rejected that idea when the cost was about $250,000 apiece plus another $3,900 a game to operate it.