The episode was aired on Saturday December 2 and was labeled as 'the Irish takeover' or 'The Saint Patrick's Day Special' by Ronan, as U2 were the musical guest on the night.
SNL follows a standard format each week, in which a celebrity takes their turn to present and appear in several comedy sketches alongside the usual comedians.
People were critical of Ronan's overly apologetic explanation of how to spell and pronounce her name.

Saoirse Ronan is 23. She was nominated for her first Oscar at 13, her second at 21. She is a goddamn supernova & has been for over a decade. So I really really wish she'd stop indulging Americans with her apologetic explanations of how to pronounce her name.

— Roe McDermott (@roemcdermott) December 3, 2017

However, one sketch featuring Ronan has received a lot of scrutiny in particular.
The Lady Bird actor plays a Mrs Doyle-esque flight attendant on board an Aer Lingus flight, upon which everyone wears knitted Aran sweaters, eats potatoes, plays the fiddle and bizarrely, brings their dogs.

During the scene, the cast attempted to put on Irish accents to varying degrees of success. In doing so, they sparked criticism for propagating old stereotypes of Irish people once held by Americans.
The Irish Times labelled the sketch as "unfunny Paddywhackery" and Irish Twitter users had a field day with a slew of memes, jokes and complaints about the 23 year old.

SAOIRSE RONAN: it was great working on this movie, I'm so proud of my nominations-
AMERICA: HOW DO YOU PRONOUNCE IT
SAOIRSE: ... seer-sha
AMERICA: EAT THESE SHAMROCKS

— A Muppet Christmas Carl (@TVsCarlKinsella) December 3, 2017

Aer Lingus themselves got in on the joke, and tweeted about the sketch in the combative style of US President Donald Trump, writing: "Just tried watching Saturday Night Live - unwatchable! Totally biased, not funny and the Ronan impersonation just can't get any worse. Sad."

Just tried watching Saturday Night Live - unwatchable! Totally biased, not funny and the Ronan impersonation just can't get any worse. Sad

— Aer Lingus (@AerLingus) December 3, 2017

I have to laugh at some people who don't seem to get the joke. ? pic.twitter.com/umOcrLA7bp

— Cian Ormond (@cianormo88) December 3, 2017

One the other hand, American audiences seemed to be totally unaware of any potential criticisms and Ronan received some good reviews.
Indiewire.com said that "The Lady Bird> star fit seamlessly into the action this week, with amazing commitment to each and every character she was asked to play... a solid utility player with great timing and attitude".
Funnily enough, vulture.com's review of the sketch regarded it as "light, fast-paced, and silly enough to succeed" and believed that "most of the SNL actors who try the Irish accent do a pretty good job with it".