Today's globalized era poses a myriad of global challenges. Nuclear proliferation and a host of environmental issues, i.e. deforestation, global pandemics, climate change, a loss in biodiversity, lower crop yields, acid rain, air pollution, all disregard national boundaries. Similarly, these issues need to be addressed globally in order to be solved. All nations have to take steps to mitigate their carbon emissions to save the planet. Especially with rising sea levels and environments becoming uninhabitable, the map of the world is sure to look different within the century. Global issues undermine individual nation's sovereignty, as individual countries are unable to solve all these issues by themselves.
Fortunately, technology and international forums and treaties provide the means to bring nations together to confront said issues. These problems have the potential to form a strong global community and create "global citizens" to address them. Similarly, through social media and the internet, there does appear to be a shared global culture emerging. However, nationalism and tribalism undermine globalism today. Strong men leaders continue to espouse isolationist, zero-sum views. Assertions such as Trump's "America First" pit nations against one another, instead of bringing them together to solve global issues.
Global citizenship is a way of thinking of oneself as a citizen of the world; one's loyalty lies with humanity. In order to be a global citizen, one must have empathy and awareness of different cultures and recognized shared humanity in them. Global citizens see themselves as being responsible not only to their country or to their religious group but to the world as a whole. Nationalism is still very much present and keeps global citizenship from becoming a reality. Today, arguably the greatest attempt towards subduing nationalist sentiments and building a global community, the European Union, appears in trouble, especially in the light of Brexit.