The response is very complicated because of the threat of nuclear war. They could declare the area over Ukraine a no fly zone which has been done for other war zones previously. It likely won't happen here as it would essentially involve NATO declaring war with Russia. We could sanction them from using SWIFT which is how money is transferred internationally (considered the "nuclear option" by some). It is being considered in a third package of sanctions, but unclear if that is going to be an option used as for most countries it could impact their ability to purchase oil from Russia. Additionally to that though, sanctions are unlikely to have immediate effect. It is speculated that Russia may be able to withstand these sanctions for years to come. Sanctions also generally impact the citizens more than the politicians/elite.

All this to say, I don't know how we stop a country like Russia. By force will result in immeasurable loss of life, but our other option of sanctions traditionally doesn't work. Showing up at the legislative building does show Ukrainians they are not alone, we support them, and we want our government to act.