Plenty of other nations almost went communist
"Mexico didn't go communist" would not have been much of an overall victory in the Cold War.
Under Carter, communism advanced in Ethiopia, South Yemen, Afghanistan, Angola, Cambodia, Mozambique, Grenada and Nicaragua.
Had the Reagan administration not adopted a policy of confrontation, most of those nations would probably still be communist. Certainly no Democrat would ever have opposed the Sandinistas, or invaded Grenada.
Add to that the Democratic opposition to missile defense, opposition to hardline positions in arms talks, and many other situations where a Carter, or a Dukakis, or a Mondale would have adopted a "moderate" stance, and we would have seen where the "dominos" would have landed.