The United Kingdom cannot fit inside the state of Texas. In fact, you could fit the UK inside Texas almost three times.
| Entity | Area (sq km) | Area (sq mi) |
|---|---|---|
| United Kingdom (Great Britain + Northern Ireland + islands) | 243,610 | 94,060 |
| Texas (US State) | 695,662 | 268,597 |
Map projections (Mercator) distort high-latitude regions like the UK, making them appear larger relative to equatorial regions like Texas. On a globe, the size difference is obvious.
Bottom line: Texas is huge. The UK is modestly sized. The UK fits in Texas with room to spare.