So many hollies!

>>I don’t know if these are all American holly, ilex opaca, or something invasive.<<

It's probably wise to identify them now, so that if they are invasive, you can dig them up. If you're getting volunteers like this, they might take over your yard.

>>None of the ones originally discovered have flowered so I cannot tell if I have both sexes here.<<

They may be too young yet. My 'Royal Family' female has berries but is about knee high and quite bushy.