If I am reading your post correctly, you are saying "Sure, the government has lied before, and I know it, but this time, it's on the level, so we should implicitly trust it."
Fool me once, shame on you. Try to fool me repeatedly, including blatantly political shenangians?
GFY, gub'mint.
I am old school and believe there should be a vital national interest before we, as a nation, expend blood and treasure on something.
There is nothing about Ukraine that meets that bar for me.
And if Old Europe can't be unassed to care, why should I? As Biden's former boss once claimed, "We'll lead from behind..."