Guess all you want. The scoreboard says 150k Germans served in literally Afghanistan.
The places with volunteer armies, they're not all going to quit. The places with compulsory armies, aka the most likely places for Russia to invade, they've been preparing for, fighting, or under the yoke of losing this exact war, for like 300 years.
I'm not saying the US should send people to die for a couple parts of Eastern Ukraine. But if push comes to shove, Europe is going to shove Russia's sh!t in. They have more economic might and more people.