[rsynnott]

That would lead to an increase in consumer prices, a decline in quality of consumer goods due to lack of competition (look at the rubbish the British car industry used to get away with due to protectionism prior to European accession...), followed by public outrage and either a swift reversal of the policy or the collapse of Europe.

And there would obviously be retaliation. Europe makes a lot of the world's things-for-making-things (like this casting system, say). The market for that sort of thing would shrink due to retaliatory protectionism, and the quality would get worse due to in-Europe protectionism.

In general, closed-off markets tend to produce poor quality consumer and industrial goods, priced too high.