You are not ignorant. This question comes up a lot.
All Roto Grip balls are submitted for USBC approval.
It is perfectly acceptable to use Roto Grip International releases in USBC sanctioned competition.
Why, has been covered many times on this site but the short answer is that the distribution, sales and marketing cycles in other parts of the world work at a different pace than they do here in the US.
For those few International balls that stay in the US...Roto Grip has you covered.
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Mike Sinek
Roto Grip Staff Manager
Kingdom member for life