Until as late as the 1850's, there were as many German speakers in Pennsylvania as English speakers, and until just before WWI it was common to hear people speaking German in the streets of any of the large cities. (There are still about a quarter million people in Pennsylvania who speak a version of German as their primary or daily-use secondary language, apparently.)
Likewise, in Colorado, there were so many German speakers that when Colorado became a state in 1876, the laws of the state were distributed, by law, in English, Spanish, and German, until 1914.
Those are the two states I know best: I presume many other states had similar situations.
The subsidies, tax breaks, etc that you're talking about? That's in the US. This is for the entire EU. But if you want to put it in US terms, maybe you should also recognize tax subisides given for oil exploration, oil logistics (keystone pipeline XL anyone?), public health concerns from smog and carbon monoxide, military protection of oil and liquified natural gas trade routes, military campaign to protect oil pipelines (Georgia most recently), cleanup efforts when some idiot decides it's a good idea to drill somewhere that no submersibles can reach, etc. In fact, the actual price of a gallon of oil in the US is somewhere in the range of $16 when all ancillary costs are factored in.
Also wealthier people simply have more resources to deal with financial trouble. They're not as likely to be split by external financial pressures, able to afford marriage counseling, possibly less likely to have been financially pressured into selecting a poor match and less likely to be looking to upgrade to a wealthier partner.
Plus one of the major things lower-income families argue about is money and how it's going to be allocated. More money, less arguments.
In our neighborhood, we can roughly estimate both income and how long a family's going to stay together by how often we hear screaming arguments coming from their houses.