What did people notice when they studied new world maps 400 years ago?

Studying the new world made them see that the coastlines on each side of the Atlantic are similar. 
Hope this helps!

It is the doctrine that the us had the right and duty to expand throughout north america. it just means they believed they had the right to expand westward and they did! they stated with the 13 colonies and then they kept moving gaining different territories throughout the years