(My bold below. Not implying anything at all about USian education or culture or the ability of US admen to underestimate their markets. Oh, no. Not me.) 
…budgie which is the common term for a budgerigar, a small Australian parakeet. A parakeet is a parrot with a long tail and a slender body. There are hundreds of types of parakeets and budgies are just one of them. So, look at you go, in one new friend you have a budgie, a parakeet AND a parrot!
Where it got twisted is that if you’re in America, you have probably only seen these little guys referred to as parakeets or, for certain color mutations, fancy parakeets. When they first started selling budgies in America (or so the lore goes), the Ad Men sat around a table and said, “we can’t possibly sell something call budgerigar to American families! They will never be able to pronounce it, let alone understand what that is!”
Then they asked themselves if there was any other name they could call it and realized that it’s also a parakeet. Patting themselves on the back, they decided that budgies would be known as parakeets, and any other parakeet would have to pick another name or a modifier!
This is how we came to have our little misnomered babies.
