The United States(hence forth called U.S.A) is one that largely does not legally allow dual citizenship, even if sometimes that law is lax or ignored if someone is from the UK, Israel , Canada and the like. U.S.A , is otherwise a style of imperialism that we have found works much better then having an army everywhere; our cultural might does the work instead. This both functions from immigrants that move here and then send stuff back to their place of origin, being thought of by some as a highest place of freedom, being a world power, and "policing the world" .
It is not mean for a country to say, okay you want to join us then you need to say good bye to your last country . We have 5 year visas if you are here to only get a education or long term visit. It really is not something that is horrible or such, think of it as sort of a boot camp that you see common within our country .
You learn about the U.S.A, you devote yourself to it, then you use your new found rights to say how horrible a country we are, or show a gushing fountain of pride in being an american citizen. I see both happen bunches, rarely do I see someone just be middle of the road, it takes a long time to get citizenry and good amount of energy and money.
As a closing argument I will say also, U.S.A has a very strong streak of self power and interdependence. While some countries view us as flag waving morons that put to much value in our country and a society that is now behind in the times. Largely as a country we work on chest beating moral compass and self imagined value. We are very aware some other countries do not like us, or may not like our way of thinking.
We just don't care.