They are pretty much similar, though an actual football (soccer pitch) field is not fixed measures, 90-120 m in length and 45-90 m in width.
In this the american football field seems more "reliable" as a unit of measure, seemingly fixed to 91.44 x 48.8 m or 100 yards x 160 feet + the borders that may vary.
https://en.wikipedia.org/wiki/American_football_field
https://en.wikipedia.org/wiki/Football_pitch
Personally I "convert" a "football field" to half an hectare:
https://en.wikipedia.org/wiki/Hectare
or 100 x 50 m.