If Americans can own pitbulls and take them to parks why can't I own a grizzly bear and take it to parks to?

Grizzly bears aren't inherently violent or aggressive like other animals, if you are abusive to a grizzly bear they will attack and snap and kill people like a pitbull if you are abusive to it.
If Americans can own pitbulls and take them to parks why can't I own a grizzly bear and take it to parks to?
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