Although the Malfoys had not been having an easy time in Britain, Lucius had never considered emigrating to America.
One reason was that Karkaroff had fled to the middle of nowhere and still been found. Another was that, like many old British aristocrats, Lucius had never truly thought much of Americans. He could accept introducing one or two American wizarding families into British society, but Draco suddenly became rebellious at this point. He insisted on marrying no one but Astoria, so Lucius turned his attention to Severus.
An outsider woman would care less about local gossip, because everyone and everything around her would be unfamiliar. To put it bluntly, by the time British society accepted her, she would already have borne children. And once she had children, would she still care who Snape truly loved?
When Narcissa was young, she too had been blinded by Lucius's handsome appearance. Only later did she learn that he was a man who could not withstand pressure. Yet she had not divorced him. Divorce was terribly undignified, and they could get by well enough as they were. She had only truly wavered when Lucius was put on trial and she was forced to appear in court. But by then, they had already lost all face. If they stirred up any further scandal, they would only become more of a laughingstock.
Aristocrats descended from the Slytherin family cared greatly about appearances. One only had to look at how they dressed to know it. Even if there was nothing worthwhile inside them, they still looked good on the outside.
This was not like commoners shouting, "You have someone else! I want a divorce!" No matter how far they had fallen, aristocrats had to keep up their airs. Rose, that impoverished British aristocratic young lady, looked down