James Kiefer summarizes the story quite nicely:
A crucial date for members of the Episcopal Church in the United States of America is the consecration of the first Bishop of the Anglican Communion in the United States. During the colonial era, there had been no Anglican bishops in the New World; and persons seeking to be ordained as clergy had had to travel to England for the purpose. After the achievement of American independence, it was important for the Church in the United States to have its own bishops, and an assembly of Connecticut clergy chose Samuel Seabury to go to England and there seek to be consecrated as a bishop.
However, the English bishops were forbidden by law to consecrate anyone who would not take an oath of allegiance to the British Crown. He accordingly turned to the Episcopal Church of Scotland. When the Roman Catholic king James II was deposed in 1688, some of the Anglican clergy (including some who had been imprisoned by James for defying him on religious issues) said that, having sworn allegiance to James as King, they could not during his lifetime swear allegiance to the new monarchs William and Mary. Those who took this position were known as non-Jurors (non-swearers), and they included almost all the bishops and clergy of the Episcopal Church in Scotland. Accordingly, the monarchs and Parliament declared that thenceforth the official church in Scotland should be the Presbyterian Church. The Episcopal Church of Scotland thereafter had no recognition by the government, and for some time operated under serious legal disabilities. However, since it had no connection with the government, it was free to consecrate Seabury without government permission, and it did. This is why you see a Cross of St. Andrew on the Episcopal Church flag.
In Aberdeen, 14 November 1784, Samuel Seabury was consecrated to the Episcopate by the Bishop and the Bishop Coadjutor of Aberdeen and the Bishop of Ross and Caithness. He thus became part of the unbroken chain of bishops that links the Church today with the Church of the Apostles.
In return, he promised them that he would do his best to persuade the American Church to use as its Prayer of Consecration (blessing of the bread and wine at the Lord's Supper) the Scottish prayer, taken largely unchanged from the 1549 Prayer Book, rather than the much shorter one in use in England. The aforesaid prayer, adopted by the American Church with a few modifications, has been widely regarded as one of the greatest treasures of the Church in this country.Here's a brief excerpt from Bishop Seabury's 1789 work entitled An Earnest Persuasive to Frequent Communion:
The general practice in this country is to have monthly Communions, and I bless God the Holy Ordinance is so often administered. Yet when I consider its importance, both on account of the positive command of Christ and of the many and great benefits we receive from it, I cannot but regret that it does not make a part of every Sunday's solemnity. That it was the principal part of the daily worship of the primitive Christians all the early accounts inform us. And it seems probable from the Acts of the Apostles that the Christians came together in their religious meetings chiefly for its celebration. (Acts 2:42, 46; 20:7). And the ancient writers generally interpret the petition in our Lord's prayer, "Give us this day," or day by day, "our daily bread," of the spiritual food in the Holy Eucharist. Why daily nourishment should not be as necessary to our souls as to our bodies no good reason can be given.
If the Holy Communion was steadily administered whenever there is an Epistle and Gospel appointed, which seems to have been the original intention - or was it on every Sunday - I cannot help thinking that it would revive the esteem and reverence Christians once had for it, and would show its good effects in their lives and conversations. I hope the time will come when this pious and Christian practice may be renewed. And whenever it shall please God to inspire the hearts of the Communicants of any congregation with a wish to have it renewed, I flatter myself they will find a ready disposition in their minister to forward their pious desire.
In the meantime, let me beseech you to make good use of the opportunities you have; and let nothing but real necessity keep you from the heavenly banquet when you have it in your power to partake of it.