What is the right engagement distance for USA BB?

Yup. You want mid-short range to take advantage of your rapid fire 5” guns and the AP on the 14” guns. I’ve found that my first and second salvos are HE at Destroyers or torpedo armed Cruisers. Then I switch to AP for enemy Battleships or any Cruiser in reach. Since the American BBs are slower than most anything above Tier II you are best positioned outside looking in. Then when you have a target separated from the herd you can turn in to keep your armor angled and close the range.

The other night I did just shy of 94k damage in my Colorado using this tactic.