If you look at the cities in US with most rapes and generally at the countries in the world with most rapes per capita, you will find some common denominators. I think it is more prevalent in certain cultures, for example Sweden has a lot of rapes per capita despite being generally held as one of world's best countries, and this largely due to massive immigration there. The government there has chosen that path and will face the consequences. Combine this with the welfare state model and a juridical system with weak punishments and you are pretty much set for a catastrophe.
I'd say that's a too simplistic view. The relatively high number of charges
made to the police for rape around here, and the lower but fairly high frequency of those charges going to court are much more reflective of what kind of actions are included under rape, in the code of law and in general talk. The "matching" of the R-word to actions and behaviour stretches wider in Sweden than in India or even in many European countries, even in the UK as Consortium was on to. You're broadly right that gang rapes around here are often committed by gangs of young immigrants and immigrants' children, "ghetto kids", not by native Swedes - but gang rapes are not really the major part of the figure of rape they appear to be in the news, not in any country I think.
It's also about how far most ordinary women feel it's within their reach to actually make a charge for rape and expect to get a serious hearing, to actually get it into court. In a country like India or Brazil, or even Russia I figure, many women would certainly feel that unless their charges are clearly backed by their husband or male relatives (brothers, uncles, parents), and supported with morals and money from that direction, there's no point in filing any rape or sexual assault charges with the police, all they would get for it is trouble and more or less outspoken shaming for "having dressed like a slut", "having pulled it upon themselves" or causing havoc for an honest man and his family.
In many countries rape at home, or within the marriage or steady relationship, doesn't count as rape
according to law, and that was standard practice in most western countries too, including the US and the UK, until a few decades ago. Any scientific data will tell us that home is one of the places where rape (or wifebeating) happens most frequently, so if the woman (or LGBT partner) is effectively expected to give in and provide sexual gratification any time the other party desires it, it's going to have a huge effect on the total number of rape charges, and a substantial imnpact on the number of rape convictions.