That depends entirely on whether the problem scales linearly, sublinearly, or superlinearly.
Your response is just another example of the defeatist attitude that most Americans have when it comes to comparisons with Scandinavian countries that have solved many of the social problems that plague the US these days. You can give no concrete reason why it would be so difficult to replicate these solutions in the US, instead repeatedly stating that it won't work because there are 30x as many people.
If we had taken the same attitude when it came to building out the interstate highway system after WW2 just because we have significantly more land area than European nations, we would have never been able to connect the whole country. But instead, we came up with workable solutions and successfully implemented them.