Non-Americans may not have heard of the #SummitOfTheAmericas, which has been around since 1994 and is pan-American.
#DonaldJTrump has characterized xyr #BoardOfPeace as a replacement for the U.N. Security Council (or even the entire U.N.). There are far fewer countries in the BOP than in the U.N..
It does seem likely that the #ShieldOfTheAmericas is the same sort of reduced Trump hegemony, but aimed at the Summit Of The Americas.