Putting aside the inspectors at that time were calling BS on the Bush administration, let’s pretend the intelligence real and not a lie.
Technically, they were claiming that Iraq had the materials to make WMDs, but they did not have the ability to launch a strike on the US. Russia has been able to strike the US for decades.
I think there is a major difference between chemical weapons and bombs that can be used for terrorist attacks versus nuclear ICBMs. One thing is to invade a country that can use chlorine gas against our troops, but placing the existence of our country and possibly humanity on the line is another thing entirely. Iraq could have potentially used gas attacks against it's population, allied populations and troops. However, Russia could nuke the hell out of NATO and cause a catastrophic worldwide famine for decades.
There's a difference between WMDs that can reach the US, and ones that can only be deployed locally. Russia has the former (and a lot of them), hence no invasion.