Nationals
First, given that the recent photos are at 174, you don't have 14 pounds of fat/water to lose -- not even close. So, if you came down to 160, you'd be giving up a LOT of muscle. Let alone coming down to 154 1/4 as you did for the Jr. USA.
Second, eventually at a height of 5'5", at the national level, you'll have to come in at 176 as a middleweight (Mark Dugdale is 5'6" and won the USA at 198 as a lightheavy).
Third, the top of Welterweight is, of course, 165 1/4 and that's the class you belong in.
Fourth, normally I would tell you to train for the mirror and let us decide what weight class you're in. However, I think YOUR eye is trained too far in the direction of extreme condition, and doesn't value mass appropriately, so I'm afraid that suggestion will cause you to over-diet. So, for the next four weeks, forget "dieting" per se. Your task is to dry out while staying full and tight. Now, a big caution given the number of competitors hospitalized after the USA is that you can't go extreme on the dehydration -- preferably, you should be under medical supervision or at least have someone close to you monitor you for signs of dehydration, in addition to your own monitoring.
THERE IS NOTHING YOU WILL ACHIEVE AT THE NATIONALS NOW OR IN THE FUTURE THAT IS WORTH RISKING, LET ALONE PERMANENTLY DAMAGING, YOUR HEALTH! Anyone who thinks there is needs to get over it.
I like your physique much better as it is in these recent photos than I did at the Jr. USA (yes, I was one of the judges there, and will be at the Nationals, but also keep in mind I'm just one vote). At the Jr. USA, you had extreme condition, but not enough mass for your bone structure.
All that said, I continue to believe that competitors need to present themselves as they wish to be. So, if the extreme condition of the Jr. USA is what pleases you, then that's what you need to do because you are the one who has to live with the outcome, not me.
That's one judge's opinion. Good luck, and see you in a few weeks.