Texas
The state of Kentucky has the longest border, being north of Tennessee, which is much longer east-to-west than north-to-south.
The state with the longest east-west distance in the contiguous United States is California. It covers a vast area from the Pacific Ocean to the Nevada border, making it the longest state to traverse.
In the west, the state of Montana has the longest linear border with Canada. In the east, the state of Michigan has the longest border, including the Great Lakes.
Width (longest distance, east to west): 357 miles
antarctica
I am assuming by east to west coast you mean the Contiguous US, or the Lower 48. In which case Texas would be the largest state.
Africa is the continent that stretches the longest from east to west, spanning approximately 4,600 miles (7,400 kilometers) from its easternmost point in Somalia to its westernmost point in Senegal.
South America
Hawaii is the widest state east to west.
Interstates I - 10 (the longest), I-40 and I-80 run east -west across the US.
The State To the west of Colorado is Utah. The state to the east of Nevada is also Utah.