Hey mg,
"A fair number of redheads?..." If you consider 10% of the population a fair number, or maybe you were just noticing it more. I have sometimes imagined an American couple travelling through Ireland, spotting a redhead and almost crashing their car to get a photo of the individual (meanwhile ignoring the more typical brunet folks).
This entire discussion seems to come down to the fact that the Irish don't look "Irish enough" for Americans. Constantly being fed the red-haired stereotype they search for some rationale to explain away the folks who don't fit their preconceptions. The Armada bit gives them "something to hang their hat on" as they say in the legal profession.
Similarly, in a discussion of "faux Irish bars" the following:
"These places were designed for a very particular market, namely, Americans. Americans like things to be the way they want them to be. If they go to an Irish pub they want their childish and simple-minded perception of what an Irish pub is to go unchallenged. To seek out truths and realities about other cultures takes too much effort."
I guess this discussion will be around as long as some Irish have to endure the Spanish Armada myth.
The Barbados spin sounds highly improbable to me: again DNA analysis could prove or disprove.