As other have pointed out, you just don't have enough barracks to build more.
I would also advice you to get of Blitzkrieg, it offer a temporary buff, it's effect last literally a day after you changed to it. And after that you just left with the penalty. It meant to be used when you alreadry are at war, either against someone you equal, where you need an edge to win. Or against multiple counters, so it's penalty have little to no effect when you start to use it.
If you going be a peaceful nation then Fortress(have more time, to wait for back up) or Moneybags(discourage raiders) is the better opitions.
I would also advice you, to switch to nuclear power in your biggest city. You using 4 slots to power that city, when you can do it with 1.
Why isen't NPO teaching you this? That hivemind of an alliance is normaly quite good forcing the most efficient methods onto their members?