“With a population of 50m people, Ukraine doesn’t need manpower - it needs American firepower and money.”
With a pop of 50 million, what they need is a will to stand up for themselves.
As events have shown, other than a few hundred radicals from the west of Ukraine, there isn’t much stomach, or support, for that.
We should help make sure that if Russia actually invades the Ukrainians aren't without the means to resist, but we shouldn't send troops or advisers for that matter. There are plenty of people in NATO who can drive to the Ukraine and teach them how to use US equipment.