It was a consideration. This is why M-Code exists - so be spoof resistant. And jamming is just a fact of life, which is why the vast majority of US military GPS guided munitions are actually GPS/INS guided munitions. They are all capable of falling back to inertial navigation, with some degradation in performance.

USG is in this position for a few reasons:

* It is actually technologically difficult to create GPS equivalent INS (or similar system). Everyone is pursuing this, not just USG/DOD. The Chinese are too for sure.

* It is true that the DoD became somewhat over reliant on GPS from a training and doctrine perspective. While they continued to develop and buy systems and munitions with INS backup, you can't operate with near total air/space/cyber dominance for ~2 decades without it somehow effecting your culture

* The war in Ukraine has been a catalyst for all sorts of technological changes, both in the West, but all across the world.

US were the first to develop GPS spoofing/jamming capabilities, so its not like they didn't think of it. I would guess that the need for a navigation system was huge, and it was unfeasible at the time to build a system impervious to electronic warfare.

It sounds like it's more that an existing problem is becoming much more frequent.

The US military always believe in the idea that the enemy is stupid or poor and cannot do anything against them.