You certainly are sanguine in regards to this and the EU's crashing and burning anytime soon. The idea of sealing the border/building a border wall has been bandied about since Reagan was president, but the American Chamber of Commerce/Open Borders Lobby has squelched any and all serious consideration. Every time.
Trump is a mover and shaker, but he's no miracle worker. I sincerely hope I'm proven wrong though.
Then call me Tadhg O'Neanderthal. Yet the EU, despite massive debt, "migrant" crises and rumblings in southern and eastern Europe, muddles along. When I see daily bank runs, constant low and medium-level acts of insurrection and martial law necessary in order for the governments in Germany, France, Italy, etc. to do their dirty work, I'll be reconstructed. I have yet to see continual instability.
As long as the magic printing presses in the ECB's cellar run 24 hours a day, people are kept fat and complacent and governments maintain the monopoly on violence, folks will mind their manners, do as they're told and worship the EU flag as if it were Baal.
I'm not going to claim it's unstable at this juncture, and that's for damn sure. Will the EU fail eventually? Absolutely, but the doomsday scenarios you post with regularity are in many instances pessimism porn.