Your question is a little confusing, but I think this will do it.

my %HASH = (
    Canada => {apples => 1, watermelons => 1, orangesUPE => 1},
    US => {applesAB => 1, pearsWE => 1},
    Taiwan => {applesZB => 1, pearsDF => 1, orangesABC => 1}
);
 
my %countriesbyfruit;
my %countries;
 
while (my ($country, $fruithash) = each %HASH){
    $countries{$country} = 1;
    for my $fruit (keys %$fruithash){
        $fruit =~ s/[A-Z]+$//;
        $countriesbyfruit{$fruit}{$country} = 1;
    }
}
 
for my $fruit (keys %countriesbyfruit){
    for my $country (keys %countries){
        print "$country is missing $fruit\n" unless exists $countriesb
+yfruit{$fruit}{$country};
    }
}
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