I'm around rank 30/40 as USF on 2vs2 random and I can tell you I never build Jackson. On team game they are a waste of money and popcap. And I have banned all the corridor maps that favor Jagt and Elef.
USF lategame is all about 3 choices:
1- Artyfest spam Calliope or Priest
3- Sherman Spam
None of them can counter heavy tank play. It is all about closing the game before OKW and Ostheer reach their critical mass.
Jackson as it is today is more than fine. Problem is USF missing tools around and Jagt/Elef. I think the modification brought to those two monsters are enough to rebalance the power equitably but USF should have access to:
1- stock late game arty, doesn't need to be at Calliope or Priest level but something that can force off your opponent from its position. USF already have something with the PakHowit but it is not enough for the late game.
2- stock heavy tank, doesn't mean to be a pershing but a heavy medium clone to EZ8, something that can take more than 4 hits before retreat, either by having a enough HP or strong armor stats.
3- stock effective AT mines and not being forced to build a m20, M7 mines are interesting but they aren't mean to be effective on the late game.
Without that, the jackson will never find its place on the game, or being too strong or too weak vs Ostheer or OKW.
There is no need to give USF both stock heavy tank and arty, something like UKF tech choice could be done. The player must choose between both and complet it with doctrinal stuff.