Speedup VBA and Apply to all visible sheets

You've got a lot of Select and Activate going on, especially at the beginning of your code....

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You are selecting a "range" of columns, then activating a specific cell, then selecting another range of columns and activating another specific cell. Looks to me as if all that is unnecessary.
To speed it up, try this...

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Totally untested (so test on a copy of your workbook)...

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Originally Posted by gmr4evr1

You are selecting a "range" of columns, then activating a specific cell, then selecting another range of columns and activating another specific cell. Looks to me as if all that is unnecessary.

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@gmr4evr1, I think you are misunderstanding what the macro recorder produces.
If you turn on the recorder then hold down Ctrl and select a few columns (say for instance A,D,F) then you will find that it produces an Activate line which is the first cell of the last column selected (in the case of A,D,F it would produce the below code).
The Column is still selected.

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Ok, now I understand that part of it, but, isn't the selecting/activating unnecessary?

Still totally unnecessary (I didn't use it either and I ignored the C8 and scroll at the end because it just looks like the OP was scanning the sheet before they turned off the recorder but I might be wrong).
The OP needed the entire columns deleted rather than a cell and I could see where you were getting it from so I thought it might be of some use to explain what I could see.

Gotcha...thanks for the info.

Not my code but unmerge your cells (and do a Google on Centre across selection).
I also don't see how your original code worked if you have merged cells.