Why do more states border the Atlantic ocean rather than th Pacific?

The Pacific is very large, so the Atlantic was predominantly a spot for shipping. With much trade going on in the Atlantic, it boosted the growth of many colonies that all evolved into their own States.

The Pacific, on the other hand, had little shipping and fewer diverse colonies from settlers, leading to larger States.

The earlier States were severely limited by transportation issues that mandated short distances between economic and political centers. As technology improved particularly the railroad the nation was able to travel farther and faster. Roads and personal vehicles, the advent of the aircraft and the bush pilot made settlement possible even in very large areas like Alaska, Crops and livestock could be shipped to population centers and to export ports.