How does an anti-ballistic shield help against tanks then?
The plan for anti-ballistic launchers in eastern europe are to protect the USA against long range launches, not to protect eastern europe from ground troops.
OMG, the shield requires personnel to run it. So when you invade a country, you need to take into account there might be casualties among US serviceman. Now this is really risky. Another point, that's pretty simple: with the shield you can nuke Ruskies and they can't nuke you. Quite a difference compared to the current situation which is a direct result of Obama being soft on Putin.