7-11 and convenience stores in general in Japan (the other big ones are Lawson and Family Mart) are vastly superior to American offerings. Almost every American who goes to Japan seems to comment on this.
It's not just Japan, it's largely Asia in general (e.g, Taiwanese 7-11's and Korean 7-11's are also so far above their US counterparts in terms of offerings/feel).
(A fun trivia fact is that like 7-11, Lawson also originally started in the USA. They only recently-ish returned stateside with locations in Hawaii (IIRC).)
I'd be surprised if there is any place where 7-11 is worse than in the US given how bad they are in here. Having lived most of my US time in PA I always either drove longer or waited for a Wawa to shop because all 7-11s were pure garbage.
The Asian equivalent of a trashy and cheap American 7/11 or Circle-K would be street vendors or a hyper-local general store/bodega with a bare minimum amount of goods.
In much of Asia (JP, SK, and TW excluded), convenience stores like 7-11 are similar luxury wise to what Target is in the US.
Probably because most Americans live in lower density cities. Fresh food distribution is a lot harder in low density areas, and that is probably why 7-11 focuses on microwavable wings and hotdogs in the US.
A good NYC bodega is as stacked as a 7-11 in Tokyo. Really good fresh baked goods and they'll cook up anything you want for you too.
With that in mind, I've never noticed a difference between the various brands of Japanese convenience stores. Lawson / Family Mart / 7/11 all seem the same to me. The only thing that ever stood out about 7/11 was that I could use their ATMs to take money out of my American bank account circa 2002 when I lived there. (The post office also worked.)