No. They are not. But I know why you think that.
First of all technically an Episcopalian Church is one that looks to bishops for leadership. There are many Episcopalian Churches in the world, ranging from Eastern Orthodox to various members of the Anglican Communion.
Now what most people mean by the Episcopalians is The Episcopal Church in the USA. This group is in a unique position. It looks both to the Anglican Church and the Catholic Church, and has special dispensations within both of them. The result is that both Anglicans and Catholics tend to view Episcopelians as being versions of themselves.
For instance a Roman Catholic priest can switch to Episcopalian and back without losing his ordination. This is true for no other Church. It is also very common for Catholics (yeah, I know there are a couple of dozen Catholic churches, most people only know the one) in the USA to switch to/from Episcopalian. (It is often joked that Catholics become Episcopalian when they want to do something bad..and this joke has a lot of truth since the Episcopalian Church allows a lot of things that the Catholics do not.)
Historically until the US revolution, many in the US were Anglicans. After the revolution when Samuel Seabury was elected bishop for Connecticut there was a problem. To be consecrated in the Anglican Church meant swearing the Oath of Supremacy to the British Crown, which he wasn't willing to do. He therefore went to Scotland and was consecrated there. But he continued to view himself as part of the Church of England.
During the 1800s the ties to the Church of England were maintained but Episcopalian practice drifted away from the Anglican and towards the Catholic. For instance their communion more closely resembles a Catholic communion than an Anglican one. I'm not sure where or when their special relationship to the Catholic Church was recognized, but they definitely have it.
Cheers,
Ben
PS I knew the broad outlines of this off of the top of my head. Most of the details I just pulled from Wikipedia. The fact about the special relationship with the Catholic faith I learned from a Catholic who was a co-worker at a previous job. He cared because his wife is an activist in the Roman Catholic Church who wants priests to be able to marry freely. He therefore knows all ways that they can already marry - and one is to switch to Episcopalian, marry, then switch back to Roman Catholic.
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)