I own one that I bought ready made and one that I electrified from a kit. Honestly, it's hard to get anything that is very good for less than $1000. As mentioned, the lithium battery is the biggest chunk of it. $2000 seems to be the price point for a "good" e-bike.
In the range of $1000 give or take, the ready made ones are going to be fairly entry level in terms of all the bike components. I don't have any brands to recommend or avoid per se. If you google electric bike blog, you will find some nice blogs that have reviews of specific models. One thing most people recommend is to make sure you like the bike itself, that it fits you and your riding style.
You won't be buying anything that violates any laws here in the US or Canada. They are treated as bicycles.