Gridiron

Wikipedia actually uses "Gridiron football" as the title of its page on what we in the UK would call "American football".

It says, 'The term "gridiron" originated as a description of the sport's then–characteristic playing field, which, until the late 1910s–early 1920s, was marked with a series of parallel lines in a checkerboard (or grid) pattern, resembling a gridiron. The grid system was abandoned in favor of the system of yard lines and hash marks used today, but the term "gridiron" has survived.'

Somewhat unnecessarily (you might think), either "AFL" or "NFL" was also accepted as a correct answer to the MQL question.