Why, precisely, "most Americans" should be considered correct on this is unclear... but let's take a look at the source. You don't cite a source for this, but it appears to be from here:
The history of Christmas trees goes back to the symbolic use of evergreens in ancient Egypt and Rome and continues with the German tradition of candlelit Christmas trees first brought to America in the 1800s.
www.history.com
Okay, so let's take a look at that article's claims. It claims at the start that "The history of Christmas trees goes back to the symbolic use of evergreens in ancient Egypt and Rome and continues with the German tradition of candlelit Christmas trees first brought to America in the 1800s." This is not exactly false, but highly misleading. If you look in the article, it refers to how (although without giving citations) how some pagans took plants into their homes. The problem is that the examples it cites are extremely old, with most from the centuries BC, and the latest being in the early centuries AD.
Then suddenly it cuts to the 16th century:
"Germany is credited with starting the Christmas tree tradition as we now know it in the 16th century when devout Christians brought decorated trees into their homes. Some built Christmas pyramids of wood and decorated them with evergreens and candles if wood was scarce. It is a widely held belief that Martin Luther, the 16th-century Protestant reformer, first added lighted candles to a tree. Walking toward his home one winter evening, composing a sermon, he was awed by the brilliance of stars twinkling amidst evergreens. To recapture the scene for his family, he erected a tree in the main room and wired its branches with lighted candles."
Notice that we suddenly have a 1000+ year gap between the pagan practices of bringing in trees and Christians doing it. It is extraordinarily unlikely that the German Christians in the 16th century were pouring over books about ancient pagan practices and thought "man, those pagans way back when sure had some cool ideas, let's start doing them!" So while one could say that "the history of Christmas trees goes back" to what pagans did long ago, it would only be in the sense that they happened to do some things that were a bit similar, not that there was any actual influence. Hence the article description is rather misleading.
Incidentally, I want to make a further comment on the claim that "as late as the 1840s Christmas trees were seen as pagan symbols and not accepted by most Americans.” But it does not seem like any of them drew any connection between it and Jeremiah 10... at least, none that I can find. As I noted earlier, I've been unable to find--even in works by people claiming that Christmas trees come from paganism--anyone trying to claim Jeremiah 10 refers to Christmas trees prior to the 20th century. Alexander Hislop's pseudohistorical 19th-century work "The Two Babylons", which is the source for a number of anti-Christmas talking points, doesn't connect Christmas trees to Jeremiah 10 despite spending several pages pages trying to claim they come from paganism.
The first person I have been able to find claim Jeremiah 10 refers to Christmas trees is John Quincy Adams (no apparent relation to the President), who in 1924 published "His Apocalypse", which claimed Jeremiah 10 referred to Christmas trees (it also claimed that the Book of Revelation declared the world was going to end in 1930, so it is perhaps not a source one should trust for proper exposition of the Bible). The person who seems to have popularized the Jeremiah 10 claim was Herbert Armstrong, a binitarian radio preacher who founded the Worldwide Church of God and, among other odd ideas, claimed the British were descendants of the Israelites. So not only does the idea that Jeremiah 10 had anything to do with Christmas trees not show up until the 20th century, the people it came from appear to have had a bunch of questionable (in the case of Armstrong, downright heretical) ideas.