In general there's been a lot of commentary on the fact that a lot of Jewish artists and creators were involved in the creation and development of superheroes, from Superman (Siegel and Shuster) to Batman (Kane, Finger, and Robinson) and so on. But in general these creations are fantasies of assimilation, of acceptance. Superman sure is an immigrant from another planet and so on, and there's something Moses-like in him but Superman was raised in America's heartland of Kansas, and his civilian identity Clark Kent is very WASP. Bill Finger was likewise Jewish, but he wanted Batman to be a Patrician WASP since he felt that suited the character since it gave him a sense of authority, and ownership of Gotham that you can't really get across with any other ethnicity. The first out and out Jewish superhero is Katherine "Kitty" Pryde (https://www.cbr.com/first-jewish-superhero/). Peter Parker being Irish American makes him in line with other Marvel street heroes who come from Irish ethnicity like Matt Murdock and Steve Rogers. And in the 60s, having superheroes come from irish-american backgrounds was rare, because usually they were WASPS. You look at the Fantastic Four -- Reed, Johnny and Sue are WASPS, Tony Stark is WASP. Benjamin Grimm was intended by Kirby to be Jewish but that was never outright confirmed until fairly recently in comics' history.

It's kind of weird that the only ehtnicity openly acknowledged in the Lee-Kirby era was Romani (who they called gypsies, a phrase that's now identified as a slur) and they used that explicitly for villains like Doom, Scarlet Witch, and Pietro (well until the latter two became Avengers belatedly). Which is kind of insensitive since Romani were also victims of Nazi genocide and this was just 20 years after the Holocaust. At the same time, the most subversive thing that Lee and Kirby did was take the Norse pantheon, which was still sullied by association with Wagner and Nazism, and make that into a lucrative global property and the defining pop culture version of that. They made the Norse gods into household names for the first time since the end of the Viking era and it was two Jewish-American vets who did that.

Spider-Man was co-created by Stan Lee, a non-practising secular Jew, and Steve Ditko, a Randian objectivist and an atheist who was of Slovakian descent. When Stan Lee decided to marry Peter and Mary Jane, he chose a secular non-denominational wedding in the newspaper, and that was followed by Jim Shooter in the Wedding Annual. The word "god" isn't mentioned there. So that's about as official as it gets that Peter and MJ aren't especially religious. So I think Peter is Irish American, that checks out, it's there in the text and it's not uncommon. But I don't think he's especially religious except in a very vaguest of senses. He talks about god and has some spiritual ideas here and there, but it's in the same way that people do that in life when they say it in general. You know when people say "oh my god" they don't actually mean God as in the Bible and so on.

I don't see why a character can't be of an ethnicity and still be universal. Black Panther is Wakandan and he's universal, as is Steve Rogers, as is the Canadian Wolverine.