I got mine originally from TV, as in my country everything is subtitled, so that means I ended up with an americanized accent (it isn't really an "american" accent because there is no such things as an american accents but rather several).

It was of course poluted by my own native language (portuguese, from Lisbon) accent.

Then I went and lived in The Netherlands for almost a decade so my accent started adding dutch "effects" (like a "yes" that sounds more like "ya", similar to the dutch "ja").

And after that I lived for over a decade in England, so my accent moved a lot towards the English RP accent. In fact I can either do my lazy accent (which is the mix of accents I have) or pull it towards a pretty decent English RP accent if needed for clarity.

By this point I can actually do several English Language accents, though mostly only enough to deceive foreigners rather than locals - so, say, a Scottish accent that will deceive Americans but Brits can spot it as not really being any of the various Scottish accents - including the accents of foreign language speakers in English (i.e. how a french or italian will sounds speaking english or even the full-force portuguese accent when speaking english, which I don't naturally have anymore).

That said, IMHO it is very hard for somebody who grew up in a foreign country speaking a foreign language to fine tune their accent so that it sounds perfect to the ears of a local, and this is valid for all languages, not just English.