The fretting in the financial markets after Great Britain's voters narrowly decided to leave the European Union (EU), a move dubbed Brexit, was less about immediate effects--there aren't any since it would take Britain up to two years to withdraw--and more about a foreboding that other countries will want out, too.
In addition, some think it likely that Scottish independence will once again be on the agenda. Scots were heavily in favor of remaining in the EU.
Centrifugal political forces are bad for business since they spell uncertainty and ultimately disruption if they come to fruition as they did in Britain regarding the EU. And, Britain, of course, isn't the only country in Europe facing breakaway movements. The people of Spain's Catalonia region have for some time sought a referendum on independence from Spain. Only last year Catalan separatists won a majority in the regional government. The movement cites cultural and linguistic reasons for independent statehood, reasons that could be asserted by many groups across Europe and lead to more instability.
The larger question is why there is building discontent with global economic and political integration not only in Europe, but also in the United States as evidenced by the candidacies of Donald Trump and Bernie Sanders.