#3 TV-movies and relatives. Most Swedes in my age have relatives in the USA, so we are used to migration and having contact with people who went to the States or still live there. So fun when they come to Sweden and will stay for a time in our guesthouse (the old house).
I bought a lot of Computermagazines in other languages, because they were interesting. The American were easier to understand than those printed and written in England. but the German were the best.
I speak American English! Its funny how we do see British english as being proper. I honestly like the way the British English sounds, there is nothing wrong with having a clean and proper speaking habit.
Though I am British there is much to be said for US spellings which are generally simplifications and better reflect how these words sound in use in both dialects.
In terms of accent I'm very glad to have a standard British accent which tends to be respected throughout the world including the US. It should be remembered that British English has far more local accents than the US which really only has a handful of major regional accents. Some of the regional UK accents are difficult for foreigners - and even those from other parts of the UK to fully understand so maybe something of a liability.
I speak standard American English, as I grew up in the US. I grew up in California so I don't have too much of a specific dialect but I do use some slang words that are unique to Northern California when I'm back visiting.
Many years ago I bought a book Amerikanskt Slang Lexikon from 1970 (ISBN 91-518-1225-8) For many years a was a member of Pixelgasm.com (sorry to tell you it doesn't exist any longer) and there they told me to use Urban Dictonary at the web.
It was so interesting to have "friends" all over the world. Every month I had visitors at my own website from about 40 countries. It was fun. On those days my website was more than 10 times as big as it is now. Sorry but so much has happend and I haven't take the time to fill the new version with material.
#12 I grew up in Dorset, but lived with a Yorkshire lass for 6 years. I find a Yorkshire accent very attractive but to survive in Cambridge and subsequently the City (of London) she had to ditch it and develop a standard accent. Whenever she spoke to her parents on the phone or we went up there she would immediately break back into Yorkshire. Accents can be a big impediment in the UK. Had a picked up the traditional yokel accent from my farming friends in Dorset I would have been ridiculed in Oxford and a career in the City would have been next to impossible.
I think nowadays your accent means less in the grand scheme of things. The increasing popularity of University for young adults means that they are spread across the country, so the exposure has definitely increased.