Not a lot of terribly surprising final results. The biggest cupset was, indeed, Monterey Bay. As a very young club with lots of genuine talent on it, it's not the most surprising they managed to get past an MLS team, though that team being San Jose means it does count for at least a little -- they're #5 in MLS West.
They weren't the only one. Wednesday night had Memphis 901 FC away at Atlanta United and managing to finish 2-1. An early lead from Atlanta United (3') was equalized by an incredibly late penalty from 901 (90+6'), and they got a second goal in extra time to put the game away.
A lot of other teams tried to play to similar results, but weren't quite so lucky against their bigger-league opponents. San Diego Loyal looked out for a lot of the game, especially with them being down 2-0 in their first half and a second half penalty goal by Joe Corona leading to a counter opportunity by Seattle Sounders to make it 3-1. A second Corona goal and a stoppage time equalizer showed SD weren't going down without a fight. Sounders got a fourth in first half extra time, Loyal got another in the second, and at the very end of the game a penalty by Freddy Montero gave Sounders the win. It was by far the highest-scoring game of the cup.
Two more near-cupsets came by way of Miami FC hosting Inter Miami, and Birmingham Legion against Chattanooga FC (NISA).
At first, you'd think it to be similar to the Atlanta game. Miami FC came to a very early lead (2'), and Inter Miami had about as late of one (89'). Miami FC got a point from an own goal in the 116th minute, and Inter Miami equalized in response. Penalty kicks went the way of Inter Miami, 3-5.
Similar symmetry happened with Legion and Chattanooga. Birmingham's goal came with a bit over a half-hour of play done, and Chattanooga equalized with about a half-hour left. With no scoring in extra time, penalties decided the result, 4-3.
MLS teams had a fairly unsurprisingly easy time against USL League 1 teams. Union Omaha, who fought incredibly hard last year for a third-tier team, were knocked out by St. Louis City 5-1, the second-highest scoring game of the night. Similarly, Northern Colorado Hailstorm fell to Colorado Rapids 3-1. South Georgia Tormenta managed to score against Charlotte FC despite a man disadvantage in the second half from a red card, but still lost 4-1 after Charlotte got a goal right after theirs. The only USL1 team to not score at all, though, was Charlotte Independence, despite on paper having a less mismatched opponent, as Birmingham Legion is only a single tier above them. No other lower-division teams scored (Tusla Athletic, Flower City Union, Chicago House).
In fact, Flower City Union's game at Loudoun United was the game with the highest goal differential, as Loudoun managed to score 5 goals.
There were two games where both teams were USL Championship and thus on paper more equally matched. In both cases the winner won by a point over the loser, and the loser had a player receive a straight red card. I've already mentioned NM United against Phoenix (after all, I was there for it). Sacramento Republic hosting Oakland Roots led to Republic getting an early second-half goal, and Roots getting the red card in second half stoppage time. Unsurprisingly, round 4 gives both the potential for cupsets, as they respectively face off away at Austin FC and home against Colorado Rapids. Rapids have had a pretty tepid start to their season with one win, 5 draws, and a loss, and so we might very well see Republic have a good shot at that upset this year. Definitely one to watch in the next round.
Regarding future potential cupsets, Loudoun United hosting Columbus Crew might be one to watch. Columbus are in a fairly solid position, but Loudoun have been outperforming most expectations based on where the team has been in previous seasons (which you'd know if you've been reading my USLC updates).
There's one other potential cupset that's admittedly a long-shot: Monterey Bay's next challenge will be against LAFC. Considering LAFC were almost certainly the best MLS team last season and got a championship title to prove it, it will be an incredible cupset if they accompish it.
We've also got a guarantee of at least one USLC team reaching the fifth round (round of 16) as Birmingham Legion will be hosting Memphis 901.