Looking back at 2016 I see that trump got 306 electoral votes. Michigan had 26 EVs, WI 10 and PA 20. trump could have lost in MI and WI and still gotten to (just) 270. So why don’t people just say is was PA that gave it to him? Why put it down to all three?
Probably the main reason is the razor thin margin in those three states. 80,000 votes the other way and Clinton takes all three. It illustrates how a candidate with over 3 million more votes than her opponent, a difference of 48.2% to 46.1% , somehow lost due to the undemocratic, anachronistic electoral college imposed on the U.S by the wealthy, slave-raping elitists who didn’t believe in democracy at all. Not even for white, male property owners who made up the electorate for the first fifty years in the land of liberty and equality.
Also the Democrats had won each of those three states in the previous six elections. On a micro-scale it was a razor-edge election.
Also just for accuracy’s sake it should be noted that Trump’s actual total was 304 - two electors that should have been his were faithless( Clinton lost 5 out of a pledged total of 232, for an actual count of 227 ). One of the reasons you don’t want to have too close of a decision in our slightly wonky system.
As Tamerlane said, the significance wasn’t just that one or all of those states put Trump over the top, it was that these states hadn’t flipped red in a long, long time. Not since 1984 or 1988 had they gone Republican. It would be like a Democrat capturing Alabama, Mississippi and Oklahoma.
For perspective, even Massachusetts and New York went red in 1984.