Texas-sized is an expression that can be used in two ways: to describe something that is approximately the size of the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Texas

Texas

Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

, or to describe something (usually but not always originating from Texas) that is large compared to other objects of its type.

Texas is the second largest U.S. state in both area and population, with an area of 268820 square miles (696,240.6 km²) and a growing population of 23.9 million.

Also means, extremely large; second only to Alaska.
It was the largest U.S. state, until Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

became a state in 1959. The physical size of the state and the bigger-than-life attitude of some of its inhabitants has led to the saying that "Everything is bigger in Texas".