This is related to the prosperity gospel, which Puritans were fully on board with. If God blessed you, you would prosper. Ergo, if you were prosperous it was because God had blessed you. Likewise, if you weren't prosperous, it was because God was punishing you. And if God is punishing you, who am I to stop it? So not only is helping your fellow man who is struggling more than you not really what God wants you to do, you're actually interfering in God's punishment of this person.

Or it could just be an excuse to be shitty to people who weren't as fortunate as you.

Americans are (generally) just shitty human beings. This has been true since the first landing of the pilgrims. Yknow, the gang who were famously religious extremists considered too extreme for 1600s Europe.

This is the natural outcome of an individualist society. Similar to how capitalism will always result in total economic collapse, individualism is a poison to society.

Even going back thousands of years, people generally helped each other out. You can go to a random village in the Russian countryside where people live in desperate poverty and they’ll share some food and water with a smile on their face. This is generally true anywhere in the global South.

People depend on communities and societies. America has systematically destroyed all semblance of the human experience, and it shows.