Because it's not about the soil, it's about the bond with your people, your history, your culture. There's a good kind of national pride we don't have - the kind that says "look what we've built! Look how we trust each other, look how we all keep things clean together, look how even when we disagree we work towards the goals that matter"
We don't have much trust in our people, our history is short and brutal, and our culture is just bits and pieces of other cultures. We definitely don't have a national goal, we rarely even feel a part of our local community. Our greatest connection is to work, and they'll squeeze out everything they can then cut us loose in a heartbeat
And that all leaves people starving for an identity, which is very exploitable
We felt that way when I was younger. By "we" I mean every American I knew with very few exceptions. I have watched that feeling wain and die over the course of my lifetime. We've made progress in areas like diversity inclusion, but we've slid backwards in so many other ways that people feel disheartened. They see the constant onslaught of the 24 hour news cycle, always reporting about politicians and corporations enacting policies that actively hurt or reduce the quality of life for average Americans, and it's hard to maintain that feeling. Add in the intentionally engineered political division from companies like Fox News and the result is a divided, unhappy, populace.