Mexico held presidential and congressional elections on July 1. Seven parties won seats in the lower house of Congress. See this story. Mexico uses proportional representation for elections to the lower house of Congress.
No session of the U.S. House of Representatives has ever had as many as seven parties represented. The Congress elected in 1914, as well as the one elected in 1916, had five nationally-organized parties represented: Democratic, Republican, Progressive, Socialist, and Prohibition. No Congress since then has had representatives from that many parties.