If the seedlings have been difficult to pull up (depending on how large they are when removed), they might be suckers instead. In that case, a "parent" tree must have been removed, damaged, heavily pruned, or otherwise severely stressed to trigger the growth of so many suckers. If there is no mature Black Tupelo tree (like in a neighbor's yard) that would be at risk of damage, then you can treat the suckers with systemic herbicide to kill the roots. Two commonly-used active ingredients in such products for this use are glyphosate and triclopyr. If you try either, use caution when applying them so only the sucker foliage is treated, as these chemicals might damage any other plant they contact.

If you prefer to avoid herbicide, the only solution is to keep cutting-down or mowing (if in a lawn) the suckers. The sooner you can remove any regrowth, the faster you can starve the root system, which has to use-up stored energy in order to produce suckers. If you cut down the suckers promptly so they have little time to photosynthesize, then the plants can't "recharge" that energy reserve in the roots and they will exhaust themselves eventually. How long the process takes is hard to predict, as it depends on how large or well-established the original tree was. If these are seedlings and not suckers, then it should not take long to eradicate them since they'll have a very limited root system for each seedling and they will not be very tolerant of mowing.

Miri