During the 1840s and 1850s, which set of immigrant groups arrived in unprecedented numbers, resulting in a nativist backlash in popular culture?

d

explanation:

the quote by walter cronkite contributes to the central idea of the text by supporting the central idea. cronkite argues that what is deemed “right” for and in america may not be good for other countries. this supports the central idea of the text, that the vietnam war was unpopular in america for multiple reasons- including cronkite’s.