> as well as the system of the US allies (EU) and if you do that, you're in hot water with those allies.
You will already be in a lot of hot water if you're in a war with the US. The countries who have the capability of doing this have thousands of missiles. A hundred of them being used to knock out some sats is nothing.
Missile launches still involve a significant cost. Firing a missile into space is not a cheap proposition.
And again, what if it doesn't work? You can only try this one time. After that, you lose your element of surprise. Your enemy now knows the enormity of your intent to do harm. Lesson to be learned from Pearl Harbor.
They don't have to take them all out at once. Just the threat of the system going sown at any time is enough to make it unreliant.