The distance from one corner of the United States (The Lower 48) to another is generally under 3,000 miles, as a plane would fly. If you were to fly along the East Coast from north to south, in a straight line, it would be around 1,650 miles. If you were to fly along the West Coast from north to south it would be just under 1,300 miles. The Gulf Coast would be around 1,500 miles. These are all rough estimates. Now, if the measurements were taken very close and accurate it would be a different story.
NOAA, the National Oceanic Atmospheric Administration, went out to measure the length of the shoreline back in 1939-40. They used a recording instrument on the largest-scale charts and maps available at that time. They measured shorelines of outer coast, offshore islands, sounds, bays, rivers, and creeks. The Great Lakes were measured in 1970. The total length of tidal shoreline includes measurements of the coastal states as well as the outlying U.S. territories and possessions.
The final result of the length of the U.S. Shoreline was 95,471 miles.
