when traveling to europe...?

does the plane go straight from the U.S across the ocean or does it go around the countries 9cuch as canada, greenland etc) in a circular path??

In my experience from New york, Atlanta, Miami, or Philadelphia, they fly just along the coast, over the water, but just close enough to land at an airport along the coast of Canada, but whether they also skirt Greenland and Iceland would depend how far north in Europe you're flying. If you're going to Scandinavia, they probably do edge the coast of Greenland, but if going to Spain or other southern European country, they probably head out over the Atlantic after Newfoundland, Canada.
If you're going from Chicago, middle America or the west, I'm not sure.

It all depends upon the country that you are traveling to. Let us say that you are traveling to London from New York. You may fly directly to London across the Atlantic. If you are flying from Chicago to London you may be flying over the Arctic. Various airlines will use different flight plans to get from one area to another. You best bet is to ask the airline personnel how your flight will fly.

All air line routes try to keep the plane so that it is close to a land that has an airstrip. It is for safety purposes.

Flying LA to Amsterdam I flew over land much of the time, crossing over the USA, Canada and Greenland, then a short hop to Iceland and only from there the plane was above sea.

Use a globe to see what is the shortest route in your case, as often what seems a round about way on a map is a straight line on the globe.