Patriotism is a funny thing, the attachment to flags and borders. But your country is your home (whether by an accident of birth or choice) and historically, culturally you can see why people identify with it. Patriotism need not be any more dangerous than community spirit, picking a team to support.
Patriotism for one’s continent seems a little further stretched, especially an amorphous one such as Europe. What are those shared cultural values? In Europe the shared history seems mainly about being at war with each other in different combinations. But for many, European is the acceptable face of patriotism: there are people who identify more as European than English. This happens in England more than the rest of Britain, because Englishness is confusing, fragmented, problematic and tainted by nationalism.
A little of that euro-love grew in the excitement and openness that Europe provided in the first years of easy and cheap travel around it, a little in the spirit of the original mods: signalling that you were voraciously absorbing new and smoother cultures, Fila and Fellini, rather than Findus fish fingers. But also Europe was used by many to signal that they weren’t party to the awful parts of English patriotism, which had come to be represented by the Union Jack.