Everybody knows that Americans say sidewalk. What UK/Irishers say is either footpath or pavement. The former is simple, and that's what we say to the kids because it's pretty unambiguous on either side of the Atlantic. The word "footpath" in this country might make people think of a trail through the woods rather than a paved area beside the road for walking on, but it'll do. Because pavement is tricky.
In the UK you walk on the pavement, but in the US you definitely don't - it's the road surface, for driving on. If you see a sign warning that the pavement is under repair, you'll want to be careful in the car, not on your feet. Don't mix them up.
As an addendum, the black stuff they put on the road is called tarmac (short for tarmacadam) in the Isles*, but asphalt (or blacktop) in the US.
And then, there's dirt. To me, dirt is dirty stuff, anything that makes you unclean. But to an American, dirt is the stuff plants grow in. They say soil as well, but that's the fancy word for it. Earth, here, is only the planet, not so much the stuff the planet is made of.
So when Americans tell their children not to play in the dirt, they don't mean to stop cavorting in the rubbish tip, they just mean not to get mucky.
*And, for people from elsewhere, it occurs to me that this quick run-down might be handy:
The British Isles consist of the two islands of Great Britain and Ireland. (Geographical)
The UK consists of Great Britain and Northern Ireland. (Political)
(Great) Britain consists of England, Scotland, and Wales.
The island of Ireland (geographical) is composed of the six counties of Northern Ireland (or simply the North) and the 26 counties of the Republic of Ireland (the South) - (political).
Does that clear everything up? Wikipedia can tell you more, of course.