For instance baseball analogies with regards to human sexuality:
(Not really safe for work!)
Non-US Dopers: Please Share Any US Culture References You Didn't *Get* from Exported American TV/Mov
When I was a kid I had no idea that “wash up” in America meant to wash your hands, because here it only means washing plates, cutlery etc.
So when a mother in a TV show would tell tiny kids to wash up before dinner it was like they only washed the plates just before using them and even little kids had to do it. Sometimes multiple little kids and their older siblings or even adults had to wash the dishes before dinner. Even adults who are guests had to wash dishes before they ate. How many plates do these people have and why don’t they wash them after eating?
In a recent re-run of Friends I saw, Chandler made some complicated baseball reference that I can’t quote because I didn’t get it. Maybe it wasn’t even complicated. I have no idea.
“Third base” as a sexual metaphor was something I had to put some real thought into as a kid, and my teenager has asked me what it meant.
“Home run” is used enough that I get the general idea and most others probably do, but it doesn’t have the same impact and requires some translation.
Then there are the times when a character (not playing baseball) touches their nose and chin or something and I think it’s a baseball reference but what to precisely I have no idea.
Well, references to British money have mystified their fair share of American readers/viewers.
Non-sexual baseball metaphors:
In baseball, baserunners and batters are supposed to look for instructions on in-game strategy from the manager or coaches (“should I swing away or bunt or take the next pitch”, “should I try to steal a base our stay put”, etc.), and these instructions are given as gestures from the sidelines. To avoid tipping off the opponents, these gestures are coded and changed over time.
A common visual joke about baseball is how complicated these gestures can (in theory) become.
Never mind! 
As in The Naked Gun. 
Or the Simpsons episode “Homer At The Bat” 
“All right, Simpson, let’s go over the signals. If I tug the bill of my cap like so, it means the signal is a fake. However, I can take that off by dusting my hands thusly. If I want you to bunt, I will touch my belt buckle not once, not twice, but thrice. If I tug this here…”
Getting to third base with a girl for example. First read that in a novel. I kinda got it involves the genitals being touched in one way or another, but I was like"is there then a first base? second base? who thought up that system???"
Then I learned it came from baseball.
In a previous thread, several people pointed out that folks would often come to the game just because it was where everyone went. You could walk around and visit/network with the game as background.
I alway thought of the ‘over’ part as meaning it was flipped and the ‘easy’ part as referring to how much total cooking was done. Sort of ‘easy on the heat’. The other two done-ness words are ‘medium’ and ‘hard’.
I can see that you’d maybe flip the egg sooner for an ‘easy’ egg, and that you’d want to be careful and do it gently. But flipping a less cooked egg is difficult, not easy, especially if you’re doing it at home, in a frying pan. So I alway thought of ‘easy’ as the egg equivalent of ‘rare’, rather than thinking of it as how you were flipping it.
Food doesn’t eat itself either /nitpick.
What I don’t get is why someone says ‘check please!’ when asking for the bill. 
I think it refers to the alumni returning to the school to catch up with each other and get shaken down for contributions in person.
Indeed! At first, I hesitated contacting the last-minute nanny service provided by my employer because they were called “pinch hitter nannies”. I wondered what type of cruel person would name a babysitting service after pinching and hitting!
This kind of thing is exactly why my large German dictionary has little sidebars explaining American and British cultural concepts in German as well as German cultural concepts in English. If you look up “Thanksgiving” in the English-German section, for instance, it’ll have a paragraph or two explaining what the holiday is about instead of just something like “Dankbarkeitsfest”.
Because the check is the bill.
That’s freakin’ hilarious!
Almost but not quite. The batter has to be in some way responsible for the run coming in.
Wiki entry.
So, if there us a passed ball or wild pitch while the batter is up, and a run comes in, the batter does not get an rbi.
To me the check (cheque in Canadian’) is what you pay with
Great thread idea. The most surprising revelation has been all of the confusion about eggs. Do people outside of the U.S. not eat their eggs cooked in a variety of ways? I mean, do you have an equivalent to an omelet, scrambled eggs, poached eggs? Is it just the language or is it the very concept?
Unless, of course, you pay in $5, $10, $20, $50, or $100 bills.*
*NB: Canadians have neither $1 nor $2 bills, just coins (“loonies” and “twonies”).