For the same reason the US pushed Saddam out of Kuwait.
The 'world order' we grew up with seems like it's strong but it's not, it's very fragile.
US protection of S. Korea / Japan / Europe is like 'propping up key dominoes' in the chain.
Wars break out sometimes fairly easily, having bullwarks ostensibly keeps them from falling down.
Obviously there are many costs and risks.
For the same reason the US pushed Saddam out of Kuwait.
The 'world order' we grew up with seems like it's strong but it's not, it's very fragile.
US protection of S. Korea / Japan / Europe is like 'propping up key dominoes' in the chain.
Wars break out sometimes fairly easily, having bullwarks ostensibly keeps them from falling down.
Obviously there are many costs and risks.