Today Britain ratified seceding from the European Union, another Western attempt to insulate itself from the rest of the world. America has its own strain of this same politics, embodied by Donald Trump and white conservative nativists. Trump's slogan, "Make America Great Again" is code for "Make America White Again," in the same way as Britain's exit from the EU is an attempt to make Britain British again. There is also a not-so-subtle Evangelical agenda at work here to make the U.S. Christian again (as if it ever were).
In all of these cases, the movement towards isolationism is motivated by fear, greed, xenophobia, racism, and outright hatred. Trump and his British equivalent, former London Mayor Boris Johnson, galvanize support for their campaigns and political agendas through fear mongering, race baiting, and perpetuating this myth that there is some "America" or "Britain" to preserve. There isn't. Countries, like human beings, are composites of many different factors--parties, forces, groups, institutions, and agendas. To subscribe to the notion of a single America is delusion, one that flies in the face of post-modernist and Buddhist thought alike.
There is no single self inside of people, no CEO or President who makes executive cognitive decisions. What we casually call the self is a shifting matrix of overlapping mental, physical, and emotional processes which interact with one another, as well as with our entire environment. Likewise, there is no single Buddhism, Christianity, Wall Street, Islam, or America. Each is a catch-all term to refer to groups that share, for the purposes of convenience, similar qualities, values, or attributes.
Trump, Johnson, and Bill Maher all have a hard time wrapping their minds around the fact that there is no single...anything. Bill Maher, known for his reoccurring indictment of Islam, makes the same mistake as Trump does; namely believing that there is one Islam. There isn't. Islam is not a single entity, which for some reason Maher cannot understand.
There are many different groups of people who claim to be Muslim, many of whom vary enormously ideologically. In terms of ethical values, I think that it's safe to say that your average Muslims resemble Christians more than they do fundamentalists who claim to be Muslim.
Trump can't recognize that and neither can Bill Maher, Boris Johnson, Ann Coulter, and many of their followers. It's worth noting that even if Trump and his ilk did realize this, they have a vested political interest in perpetuating the myth--they win votes by scaring people into thinking that their nation and religion is under attack.