In plain English, the best Mexican league teams are better than their MLS counterparts. But in their lower tiers the two leagues are now competitive with each other.
Liga MX uses a single table of 18 teams that play two annual tournaments (Apertura & Clausura) resulting in two champions per season. The season opens with the apertura tournament (opening tournament- running from July to December) followed by the clausura (closing  running from January to May).