The domino effect isn't that it never stops, its that once it starts then it spreads unless someone else comes in and stops it. Proving that the whole world didn't fall to communism doesn't prove the domino effect isn't valid. Look at any country that solidly fell to communists and you can immediately see major state sponsored insurgencies forming in neighboring countries. Not a coincidence, its a design in communism and a stated goal of all of them, to spread communism. Once one country falls, their efforts are to consolidate power in their own country (through mass murder) and then exporting terror through support of neighboring insurgencies, which ends up causing what can be described as dominos falling.It didn't stop? So Thailand, Burma, India, Nepal, Pakistan and so on all immediately went Communist?
A better example I would use would be dealing with a gangrenous limb. Or a sick cow living in a pen with a herd. But domino works too. But its political concept based on a metaphor, so yeah, its not going to be 100% accurate in describing what actually happened.
"I'm going beat the crap out of you!"
"No you wont, because I just went to the bathroom and successfully evacuated myself!"
"I'm going to knock your block off!"
"No you wont, because I don't have a block on my body!"