I don't see this effect you mentioned.

$ LC_CTYPE='en_US.UTF-8' perl -Mlocale -le'my $ch = chr(0x2660); print
+ length($ch);'
1
$ LC_CTYPE='en_US'       perl -Mlocale -le'my $ch = chr(0x2660); print
+ length($ch);'
1

$ LC_CTYPE='en_US.UTF-8' perl -Mlocale -MEncode -le'my $ch = chr(0x266
+0); my $bytes = encode("utf-8", $ch); print length($bytes);'
3
$ LC_CTYPE='en_US'       perl -Mlocale -MEncode -le'my $ch = chr(0x266
+0); my $bytes = encode("utf-8", $ch); print length($bytes);'
3
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Could you provide a suitable test? I'm not all that familiar with locales.