As always, the linguistic and cultural divide between US and UK is significant in what "middle class" means.

At no point in American history was "2 weeks of holiday abroad" a norm for middle class Americans. In 1990, only 4% of Americans even had a passport. By the year 2000 that had grown to 17%. Today it's 42%.

That means Americans today are 10x more likely to have a passport for international travel than they were 30 years ago. In other words, it would have been incredibly rare for a middle class family in the 1980s to go to Europe for vacation. Meanwhile, it's not that rare for a lower-income American to go to Mexico or the Caribbean today.