As long as you were of sound mind when you signed the DNR (and presumably a doctor certified you as such when witnessing the DNR) then I think medical professionals are required to follow your DNR irrespective of the circumstances or method surrounding your death.
But that is just my layperson understanding, you would want to find a more definitive answer than mine before taking any final steps.
EDIT: Additionally, suicide is
not illegal in the USA. So the issue for medical professionals is not whether they risk becoming an 'accessory' to your suicide (which they do not) by following your DNR and withholding resuscitation. It is whether your decision to be DNR is made with sound mind.
As above, my lay understanding is that as long as the DNR was made in sound mind, it is irrelevant whether the subsequent suicide attempt was (arguably) not made in sound mind. But definitely check this yourself, and I am happy to be corrected on this.
SECOND EDIT: @Genetics, it seems my original clear-cut opinion above (now struckout) was unfortunately incorrect. For USA see examples of some relevant viewpoints here, here and here.