Firstly, America is a continent, not a country. Secondly, movies have romanticized the United States. And, lastly, if you were fleeing something much worse than the U.S. like famine or war, you would rather suffer here than there. Not everyone who "risks their life" to enter the U.S. remains here. Some people will go through the backcountry in the northern part of the country and enter Canada. There are parts of the Canadian border that aren't protected.

Mainly because American interference/ colonialism has wound up bankrupting their own countries

Have you seen the absolutely terrible conditions that they are fleeing? Most Americans would be crying in the corner begging for mommy if we had to go through half the shit that some of these immigrants go through. In the end, our fucked up dysfunctional country is still better than theirs form a humane point of view. Or at least it has been. Not sure for how much longer.