I was going to say I knew someone in the US with that name, but remembered it’s an English guy!
OK, from the list, the only ones I personally have never heard in the US are:
Alfie
Rhys spelled that way
Kian
Finlay I haven’t heard of for boys, but have for girls. Ryan is getting popular as a girl’s name too.
Wow, a girl. My son’s name is Aaron, and people often pronounce it the same way they pronounce Erin, which is really annoying, since there’s an Erin in his pre-K class. He doesn’t seem to care though.
Celtic names are very popular in my son’s daycare. We’ve got Declan, Liam, Ryan, Meaghan, and my favorite, Colm. Colm, at least, is the son of someone actually from Ireland and goes to visit family there every year, so he gets a pass. Liam’s last name is Polish, I think, but I suppose his mother could be Irish. Celtic is just very trendy.
“Aidan” is a pretty well-attested name: actor Aidan Quinn, John Corbett’s character on Sex and the City, oodles of toddlers nationwide 
“Rhys”, AFAIC, is essentially the original form of “Reece/Reese”. Not an unknown first name in the U.S. … but an uncommon one.
“Alfie” and “Archie” are, in the U.S., reminiscent of mid-20th century nicknames.
Interestingly … “Kian” (as “Kyan”) and “Kai” are the names of two of the five Queer Eye for the Straight Guy fellows.
“Nia” is not too uncommon, though it is marked for certain ethnic heritages (Greek, Hispanic, African-American).
Many of the names being mentioned as UK-specific are known – even popular – in the U.S. in a different form. If “Catriona” is a form of “Catherine”, that’s an example right there.
:dubious:
“Jeremy” was immense in the U.S. for boys born between, oh, 1965 and 1980. Mabe it’s out of fashion now … but at one time, it was huge.
Did someone say above that “Tony” isn’t common in the U.S.? Gotta disagree there. It might have a regional/ethnic following … Italian-Americans living in the northeast (cf. “Sal(vatore)”, “Vinny”, and “Dom”)?
Are Erin and Aaron supposed to be pronounced differently? I’ve always heard them pronounced the same way (AIR-on). In high school, I had two friends named Aaron and one named Erin. To avoid confusion, we called the Aarons by their last names, and Erin was called Vera (the name she’d picked in German class).
Yes, for most speakers: “Erin” begins with the vowel commonly used in “bet” … “Aaron” begins with the vowel used in “bat”.
If “bet/bat”,“pen/pan”, etc. are homophones in your region’s accent … then none of the above will apply.
I’ve never heard of Callum (is that like column or is the a pronounced as it is in apple?) or Finley/Finlay.
Kieran seemed to become more popular when Kieran Culkin started appering in movies.
I didn’t see anyone mention it yet, but the only three men I can think of offhand named Kim are all English.
… ah, the surname “McCallum”! Putting 2 and 2 together here 
[jayne]“Of course she has a name! I call her Vera…”[/jayne]
When my sister (English) was having her sprogs about 15-20 years ago, she thought it was v.cool and unusual to give her kids all celtic names. This was uncommon then - my parents thought it was strange if not a little embarrassing/common, and most of us had trouble pronouncing and spelling some of them. Now they’re all common as muck. Well, maybe not so much the second one, outside Wales.
They are:
Rory (uber cool name, I still think, so manly) (Scots)
Rhiannon (Welsh - ree-ah-non)
Callum (Scots)
Leah (Irish?)
I have a male cousin (in his 50’s?) named Kim. Ah, the exception that proves the rule!
I’ve encountered it only once here. A friend of mine was dating a girl named Catriona a little while ago. Her father was from Scotland and her mother was from Vietnam. When I pronounced it “Katreena,” I was corrected and told that the correct pronunciation was “Kat-ree-OH-na” and that my error was a “common mistake.”
For most speakers, really?
I believe that for most Americans (and, if not, then for most non-Southerners west of the Appalachians), the distinction isn’t made – the vowels in “bet” and “bat” (and “bait” also) merge before “r,” so Erin/Aaron, err/air, Mary/marry/merry – no distinction.
“bet/bat” don’t have to be homophones for Erin and Aaron to be. In much of North America including nearly all of Canada, /æ/ as in bat is not allowed before an r. So merry, marry, and Mary are all homophones (“merry”), as are Erin and Aaron (“erin”).
A stereotypical farmers name, no less
How funny. When I visited England twenty-five years ago, it seemed every other male was named Trevor. Now it’s not even in the top 100.
A as in apple, emphasis on the first syllable
How 'bout “Ridley”?
I’ve only heard of the one, Ridley Scott, the British director of Blade Runner.
I have a friend whose daughter is named Catriona! Interesting…I did not know that it was a Celtic name.