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Removing the leaves takes away the ability for the plant to feed itself.
Here is an article on controlling Pampas Grass.
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/pampas-grass-removal.htm

It's normal to see uneven new growth while it's still early in the growing season, but your grass may be starting to get overcrowded depending on how old the plant is. Thinning it out will have to wait till you perform annual pruning this year, but for right now you can try adding some fertilizer to the area around where there is no new growth. This article may help you:
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/pruning-pampas-grass.htm

It can absolutely be split, but get ready and make sure you have heavy duty gloves and clothing, because Pampass Grass roots can only be cut with a saw or axe. This article may help you: https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/pruning-pampas-grass.htm

This can be a common growth pattern for Pampas Grass, especially in a more wet location.
Many people will dig up and divide the Pampas Grass when this occurs.
This is not easy task!

Here is a few links with more information.

https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/pruning-pampas-grass.htm
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm

You might have to dig somewhat deep with a large shovel to remove the whole clump, but once you do, this should be a very effective way to remove it. Pampas grass does not spread underground by rhizomes or runners, so as long as you remove the entire root ball of the plant, you will be done with it.

Spring is typically the best time to plant Pampas Grass in the U.S. There's a link to the USDA Hardiness Zones in this article so that you can double-check what the optimum planting season is, and some good information on growing Pampas Grass:

https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm