No, a house isn't a national investment. Your ability to have a house is not beneficial to me.
However, an economy where workers are more productive is beneficial to me. More productivity means bigger economy, which means less people relying on government services, which means more people with money to spend.
People who go to college are on average more valuable than people who don't. Know how we know? Because they make more. Economic value is reflected in salaries.
Not to say that we don't need all kinds of workers and indeed some people don't belong in college. However, if someone would do well in college, I don't think cost should be a barrier. And no, loans is not a suitable remedy, because going into debt is not possible for some people who are economically vulnerable.