There's a reason why we wear pads.
Just ask any Rugby bloke who has been exposed to former American football athletes who are new to Rugby. They'll tell you about how they hit and how they, typically, break something (on two people) -- if they aren't warned first that they cannot hit like that.
With pads, you can increase the sheer kenetic force without breaking something. It's not being a pussy, it's called fun. At least that's what one British immigrant said that I played with in high school during his first, spring training, and playing "hamburger" for the first time (2 linemen + 1 back on each side, offense and defense, on a 5 yard wide "field"). "Now I know why you Yanks love this" after his ass was thrown back in the air about 5 yards.
The next time you watch an American football game, remind yourself how much we must be "pussies" when someone's body going flying through the air. And not because he jumped, but because he was literally hit with a kenetic force that launched his 200-250lbs. body into the air at several G forces.
There's a reason why shoulders are separated regularly in American Football. Because it often delivers several thousands of lbs. per square inch, enough to launch another body not merely backwards, but in the complete and opposite direction it was traveling. That's just a shoulder.
The best way to tackle is to not merely hit your facemask dead center on someone's number, but use your neck-chest (take your neck exercises seriously when warming up, and never put your head down, always up) along with the "launch" of your legs into their body, "jacking them up" and pushing them backwards. That can easily be a total, kenetic force spread over several square inches (possibly a square foot) that could never be attempted in Rugby.
Again, I love Rugby and its toughness, and I even played it in college (we didn't have an official, varsity team at my Alma Mater, just some club associations). But American football is about the sheer kenetic forces you can deliver, because you're wearing pads, and it is beyond hard on your joints. But damn if it isn't more fun because of it! It's like bumper cars with bodies, only bodies too can have structural failure.