No, you cannot change the width of a single cell, that's a concept many Word
"table" users would love to have. But it would create far more problems than
benefits.
If you would like the contents of a cell to display across more cells, I
also suggest you RESIST the urge to use the "merge cells" function, since
that inhibits a lot of other useful Excel functions, too.
Best solution is to highlight the cell and the cells to the right you want
to include, and select FORMAT > CELLS > ALIGNMENT > HORIZONTAL > Center
Across Selection.
Is that something you can work with?