Feels like you're addressing two different topics in one comment.

Legally speaking, a one person company can address the whole EEA market. From a marketing/sales standpoint yeah, sure, it's probably hard to address culturally different markets like Portugal, Poland and Sweden.

But it does not have much to do with regulations, especially not ones decided at the EU level.

I'm all for better integration but diverse cultures are here to stay....

Sample size of one, but done business in Italy, Spain, Belgium, France, Switzerland and Germany: main issues were not regulation related...