Japanese Robots in the classic sense are superheroes. They're either flying things on rocket packs (IE, Gundam, Zone of the Enders, Gunbuster), Ginormous (Gigantor, Sentai Shows), or Rollerskating WTF. Most of these pretty much violate physics, and go superfast.
American Robots, while influenced by Japanese ones in the last few decades, tend to either be hulking slow (Mechwarrior thing) or focus more on agility but without speed or physics violation. So, Battlemechs in the artwork and cinematics are moderate sized, surprisingly agile, and not really terribly fast. They don't turn on a dime or change vectors quickly, but can bob and weave and do that sorta thing. Starship Troopers power armor or Transformers arent particularly fast, but pretty agile. Most everything else does seem to be a redrawn tank though, because that seems 'most reasonable' to our suspension of disbelief, compared to a 50 foot tall samurai with a lightsaber.
So maybe an American-robot game needs to be about bobbing and weaving with cover? Oh god. Stickycover. We just turned Mechwarrior into gears of war.Seriously we can't even get a Mechwarrior game that lets the robots extend their arms out to shoot their guns. Or even do what the Thor in Mechwarrior 2's intro does where it casually steps around a rock face while pointing its arm out to take a potshot at the Mad Cat.
Cherry picking examples is just fucking sad; there are whole shows about robots so low-end that they travel to the scene of action on the back of a truck, Gundam traces robots from experimental space-fighters not very useful on the ground to absurd heights of agility, etc. Oh noes, Evangelion! 
