UA could have considered EWR-ICN but doubled down on SFO-ICN. Ditto for ORD-ICN. Korean Air, for a long period of time, even when they were the avoid at all costs airline given safety, have dominated US-South Korean flying, one of the reasons why the DOJ refuses to consider their merger with Asiana despite all of the other important regulatory agencies approving after concessions. LAX-ICN would not have Russian air space issues. If the Korean/Asiana merger goes through and reduces LAX-ICN traffic, maybe UA will consider it. GUM-ICN using Air Mike might not be the most competitive product offered even if they are competing with LCCs in South Korea but the demand is there may be worth the shot especially if UA is willing to flex using Air Mike on future NRT-CEB.

These are good points. KE is larger than OZ and DL has more routes to ICN than any other US carrier, so Skyteam traffic dominates that market. If the merger goes through, this would be a loss for *A network and for its users. Either way, ORD-ICN on *A would be a very good addition as that isn't covered yet, with LAX/EWR being considered if that merger does go through anyway.
Worth mentioning, Air Premia (YP) has entered the US market so at least there is more competition in this market.

The entire 738 fleet including the GUM/Air Mike units are being retrofitted with NEXT interiors, with one GUM plane currently being converted. Although this is a complicated process, by a few years UA should have a more competitive product by then as the project finishes.

United needs to launch DEN-AMS. It was rumored to launch right before COVID.

Agree. Emirates (getting off-topic) hasn't added a U.S. destination in awhile (and dropped FLL) and I am always hoping they would serve DEN, PHX, or LAS. United DEN-DXB would be even better, opening up connections to the southwest as more convenient options from DXB than backtracking from LAX/SFO or trudging through ORD/IAH only to face a three-hour connection, or more if on UA to EWR. Although UA's tie-up with Emirates is limited, having a second feeder would be nice, though maybe not in Emirates' interest.

Emirates just added a new 5th freedom route between MIA and BOG. Not a new destination, but new service nonetheless.

I smell a battle with AA brewing.