Yes, the Seattle Sounders beat UANL Tigres. There's a reason that felt so amazing: Because it was. It was the first time that a Major League Soccer side beat a Liga MX side in the knockout rounds, and MLS teams have only done so twice in fourteen tries. For all of Don Garber's wishes, the talent level in Mexico is greater than the talent level in the US and Canada.
Sure, the gap might be closing, but it's still not close. Despite everything MLS is doing to improve, it's just the second best league in the region, by a variety of measures (CONCACAF Coeffecient, SaH League Rankings, tBG League Rankings).
It's not just that Liga MX is better than MLS. It's also that Club América is a damn good team.
They won the last CCL. In fact, they've won it, or versions of it, six times. This includes the 2014-15 title they earned by beating the Montreal Impact. They hold 13 Liga MX (or its predecessor) titles.
Yes, they are only 3-3-1 +5 in league play right now. Yes, they only drew 3-3 in their last match despite having a 3-1 lead at one point. But that last match created a small issue for Seattle. Oribe Peralta and Carlos Quintero were both red carded. That means they won't play in the next Liga MX game and they're almost certain to play here in CenturyLink.
Peralta you may remember because he has played against the Sounders four times, and scored once. Oribe has 20 CCL goals, an Olympic Gold and a Gold Cup title. Quintero has only faced Seattle in the CCL twice, also scoring once. Like Peralta he has 20 CCL goals.
Part of the appeal of the CONCACAF Champions League is that it is a test against the best teams in the region. In Club América the Seattle Sounders face the best team in the region. América will likely crush Seattle, because that's what Mexican sides do to MLS sides.