I was talking with my brother last night, and the Ukraine topic came up. He doesn't believe Russia will invade (nor do I) but we both think it's possible, and it is.
That led to a discussion of what the US would do if China and/or Russia, Iran, North Korea started planting troops and bases in our back yard.
Places like Mexico (China could own that country in a minute), Cuba, Venezuela.
That would be the equivalent of NATO admitting the Ukraine, on Russia's doorstep.
The US would be outraged. Just like Russia is outraged.
Our border is wide open.
It would be pretty easy to infiltrate, and frankly, it's 99.9 percent likely that it's already started.