The people who are "anti-socialism" see road building, national defense, and policing as "the government's job" and see healthcare and other social services as "not the government's job". Hence national defense is not considered socialist, whereas single-payer healthcare is considered socialist.

I get that you think this definition is wrong, but you're in the minority here. Both self-identified socialists and anti-socialists in the US consider social welfare programs to be socialist.

https://berniesanders.com/democratic-socialism-in-the-united...

"Social Security, which transformed life for the elderly in this country was “socialist.” The concept of the “minimum wage” was seen as a radical intrusion into the marketplace and was described as “socialist.” Unemployment insurance, abolishing child labor, the 40-hour work week, collective bargaining, strong banking regulations, deposit insurance, and job programs that put millions of people to work were all described, in one way or another, as “socialist.” Yet, these programs have become the fabric of our nation and the foundation of the middle class."