Yes, but in each of those fights, humanity's response was pretty limited by fear of collateral damage or lack of manpower on the scene.

If it came to a real war... You'd be looking at hundreds of thousands of infantry pounding those little heat guns into Megatron. I don't think he would enjoy that.

If humanity got to the point of desperation to start using Stalingrad tactics... Decepticons would not last long if each little heat gun has even a one in ten thousand chance of injuring.