Maybe. Some potent antacids can reduce the ability to absorb iron. If iron deficiency is causing anemia, and the anemia is not getting better on appropriate doses of iron, an antacid might, at least in part, be a problem. If there is ongoing blood loss or high iron requirement, from, say heavy menstruation or pregnancy, the amount of iron being taken may be the problem.
Contributes somewhat. Proton pump inhibitors (ppis) prescribed for gerd can interfere somewhat with both the absorption of iron and vitamin c (used in iron absorption). If you are taking iron supplementation and a ppi, it might take longer for you to restore you iron levels to normal. There is no data, however, to suggest that ppi use causes iron deficiency in someone not taking iron supplements.