When I was younger, I associated nationalism with country formation. Poland and Czechoslovakia became countries after WWI, India and Pakistan (and later Bangladesh) achieved statehood after the British left India, and Slovenia and Croatia after the break-up of Yugoslavia. Nationalism was always a factor. Each nation wants its own country. Notice how the Kurds (famously the largest group without a country) keep fighting for independence. So it seems like nationalism should lead to more countries.
However, the rise in nationalism could well weaken organizations such as the EU and NATO, indeed there are indications that this may already be occurring. And those organizations probably benefit small countries more than large countries. A small country lacks a big enough internal market to achieve maximum economies of scale, and hence it benefits greatly from access to a big free trade zone. And obviously Estonia would have more trouble defending itself from Russia than would France or Britain (and not only because it's closer.)
In that case, do doubts about the survival of the EU and NATO make places like Scotland and Catalonia less likely to seek independence?
What do you think?
PS. This NYT article discusses 10 potential new countries. The article if full of tidbits for lovers of the arcane:
(Tuvalu recognized Abkhazia in 2011 but retracted its recognition in 2014).