I'm not making America sound broken. I'm telling it how it is. Ask the millions of people trying to get by on minimum wage jobs with no healthcare, drowning in debt, many facing eviction.
Lots of people want to come to America because in many cases, America offers a better situation than what they are currently experiencing, be it war, violence or poverty (many instances of which the US had a role in instigating through destabilizing these governments). Just because life in America may offer a better situation than what many people currently face in other countries doesn't mean America is without its own worsening problems. A worse situation somewhere else doesn't negate a bad situation here. Both can be true.
As for why people aren't leaving the US. From the comments on this post, some people have left. Others of us stay because this is our home -- our familes are rooted here, we are part of communities, and we don't believe we should have to leave this country because of the injustices and oppression it is perpetuating. We the people want this country to be better. That's why we critique it. We know it can be better.
Also, as others have pointed out, the issues I raise here are not isolated to the US but are global problems.