Are these tent caterpillars?
These are not tent caterpillars, which only appear in spring and create tent-like webs.
These are yellownecked caterpillars, a common late season caterpillar, notorious for the gregariousness and how they form a U shape. https://extension.umd.edu/hgic/topics/caterpillars-trees
These late season caterpillars are crucial food for birds preparing for winter. These late in the season they do not do significant harm to trees that have had plenty of time to carry on photosynthesis all summer and can afford to lose a few leaves. On young trees they should be removed. They can be pulled off (with gloves) and drowned in a bucket of soapy water, or cut off.