When I saw the episode description about DEO weapons getting out to the public, I was hoping that the weapons designer would be John Henry Irons. It'd be cool to add Steel to the Arrowverse, although I guess he'd be a bit redundant with Guardian there already.
Interesting that when Arrow did a gun-control episode last year, it tried hard to strike a middle ground, but this episode, while trying to give both sides a fair hearing, ended up taking a firm stand against guns. I guess the difference is that it's after Parkland, with a stronger sentiment among many Americans that enough is enough.
Meanwhile, isn't it a bit contradictory for Kara to say that Argo was the city where she grew up, and that it was rebuilt almost exactly, when last week she didn't recognize it at all when she first arrived? And it certainly doesn't look like the city where the Krypton flashbacks in season 1 were set.
Also, according to the Arrowverse Wiki, it was stated or implied at some point that birds didn't exist on Krypton, but in the scene shot in the Bloedel Conservatory (the geodesic dome), there was a shot where a bird hopped between branches in the foreground.
It also surprised me that Kara's outfits didn't have the El crest on them, when we've seen before that the family crests are ubiquitous on Kryptonian clothing. I guess maybe they hadn't had time to make custom outfits for her, so she was wearing something more generic.
It amuses me that the boy Mon-El cured with his future tech is named Val, which on Syfy's Krypton is the name of Seg-El's grandfather (Val-El).