I'm not sure I can actually add anything to this discussion, but I'll try to put in one place what I believe has already been said by others.
1. The USBC (otherwise known as the Open Team Trials - the name United States Bridge Championship was a vain attempt to garner some publicity - maybe newspapers would be more interested in writing about a "Championship" than a "Trials" - it didn't work, but we kept the name from inertia) is indeed a completely open event. Any team of 4 US citizens or residents can enter. If they aren't already USBF members, they have to join USBF and pay dues. If they aren't citizens, they have to demonstrate that they are permanent residents and haven't played for another country within 3 years. But essentially anyone can play. I happen to agree with Uday & Danny that it's a great event to play in. The one thing I regret about helping to run it is that I am no longer able to play in it, even though the best I ever did when I did play was reach the Round of 16.
2. When the Team Trials were first changed from a very limited event (4 teams played - the winners of the Reisinger, Vanderbilt, Spingold and Grand National Teams) to an open event, the ITTC (International Team Trials Committee, then an ACBL committee, now a USBF committee) decided that performance in the major championships during the year before a Trials should give a team an edge in the Trials. I do not remember whether the GNT was one of the "Major Events" at the beginning, but now it's only the Vanderbilt, Spingold & Reisinger - a good thing for me, as it means that my husband can "afford" to play with me in the GNT, although of course that was not the reason it was removed from the relevant events - that was because it was considered unfair to teams whose members happened not to live in the same District). So the ITTC set up a scale of Positioning Points that are awarded for finishes from 1-16 in the KOs and from 1-14 (making the Finals) in the Reisinger, and a number of PPs required for byes to each KO stage. A bye to the Semi-Finals requires, in addition to the number of PPs, a win in one of the 3 events. A few years ago, the committee decided to add the previous year's Trials to the events that award PPs. A year or two later, it decided that PPs earned in the previous year's Trials should count only for a bye to the Round of 16.
3. Over the years since the Trials became open, there has been a lot of discussion in the ITTC about exactly how byes should be awarded. I am sure there will continue to be discussion of that issue, and the ITTC, like the Trials it governs (the ITTC is responsible for Conditions of Contest for the Open Trials; the WITTC is responsible for Conditions of Contest for the Women's Trials; the SITTC is responsible for Conditions of Contest for the Senior Trials) is open to anyone. If you want to join in the discussions of exactly how byes should be awarded, you are welcome to attend meetings or participate in the committee's email discussions, which are very extensive. Two years ago, when the committee was discussing the format for this year's event, there was a lot of discussion of whether it would be better not to have byes to the Semi Finals in a year in which two teams are selected. Some of the committee's more mathematically inclined members even did analyses of the odds of this, that, and the other. After discussion, the committee voted that there should still be Semi Final byes, but if I remember correctly, increased the number of PPs needed for a Semi Final bye.
4. The primary reason to award byes is in order to include the major NABC events in our selection process. The ITTC believes that means we are more likely to select our best team(s) for the World Championship. And much as we want to run a quality event that everyone can enjoy playing in, our primary objective is to select the best team to represent the US.
I doubt that I've added much to the discussion. Now I need to get to work on things like the schedule for the Senior Trials, which starts on July 6th in Las Vegas. If you live in Las Vegas and would be interested in being a Vugraph operator for some of the sessions of the Seniors, send me an email
Jan Martel, who should probably state that she is not speaking on behalf of the USBF, the ACBL, the WBF Systems Committee, or any member of any Systems Committee or Laws Commission.