I once saw a meme about how if you told someone from 1950's America about the economic inequity today they would assume that the USSR won the cold war.
McDonald's prices have far outpaced inflation. When I was in college a Big Mac was $0.99 and minimum wage was $4.25. If we were just dealing with inflation then a Big Mac would be $1.66-$2.00, depending on how you calculate it.
The Nazi and KKK backed candidate won the 2016 election and is still a serious contender this year. Also the hate for the gays and people of color is associated with the party that embraces the nazis. That side also led an insurrection and took over the Capitol building while flying the battle flag of the confederacy with many hiking to capture high ranking politicians while they were counting results which likely would strip the nazi-backed party of the presidency.
They used phones to talk to people then too. You have to explain that you use something called a phone which is actually a tiny computer, to type out short messages, and send them through the air to the another person's phone, like a magical fax machine/typewriter combo.
Notializing around the dinner table with our electronic devices. They might think we have implants that allow telepathic communication. And after 70 years, no, we don't have flying cars, nor manned interplanetary rockets, nor world peace - although we haven't blown everyone up with the bomb yet. And yes, Ronald Reagan was the president.
Well here's a less obvious one that would probably confuse them, we have black people starring in the MLB who speak Spanish, and have green eyes.
The internet and cell phones would be easy enough for them to grasp, they had examples with Dick Tracy. Although I think they'd really struggle with the culture of the internet, and what we've chosen to do with it.