"These items were sold by third party sellers on our open marketplace, and were not offered directly by Walmart," a company spokesman said. "We're removing these types of items pending review of our marketplace policies."
The controversy highlights a challenge of doing business in a country increasingly polarised by politics, where supporters and critics of Trump have become more vocal in pressuring companies with boycott threats when they appear to be taking sides.
Other brands that have aroused howls on social media include athletic clothing and equipment brand Under Armour after its chief executive praised Trump, and sporting goods chain Dick's Sporting Goods that restricted some gun sales.
Neil Saunders, managing director of consulting firm GlobalData Retail said Walmart's decision to remove the anti-Trump merchandise made sense given the company's profile. Most e-commerce consumers do not make a distinction between items sold directly and those offered by third-party vendors.
"A lot of the stores are in locations that are probably fairly Republican," Saunders said. "They do need to take action because it could alienate a large portion of their customer base."
And he said the idea of impeaching the 45th US president went a step further than the MAGA gear, which expressed support for Trump and could be offset by equivalent products on behalf of Democrats.
Walmart in 2017 also removed shirts with the phrase "Rope. Tree. Journalist." implying reporters should be lynched, saying the items came from a third-party vendor and violated company policy. And the store in 2015 announced it would no longer sell items promoting the Confederate Flag.
Trump has not shied away from entering the fray, chastising US companies via tweet from transgressions ranging from investing overseas, to moving production to foreign sites, to laying off workers.
"No need to boycott. @Walmart has assured me that the merchandise will be down as soon as possible," Parscale said on Twitter. "It was not deliberate.
Amazon currently offers dozens of products with "Impeach 45," or similar phrases, such a "86 45" or "Resist 45." Amazon's site also offers a wide assortment of "Make America Great Again" and other pro-Trump gear.
Saunders said the difference in approach underscored the gap between shoppers of the two companies, with Amazon consumers tilted somewhat more heavily towards cities and other progressive areas.
However, the Walmart-owned website Jet.com still sells a variety of items under the more lighthearted "Impeach the Peach" logo that features a likeness of the US president on travel kits, guitar picks and other items.
Saunders said the clientele at Jet.com is probably closer in spirit to Amazon than Walmart.
"Walmart and Jet are very separate brands," he said.
"With Jet.com there's far less risk because the client base tends to be younger, more urban, probably less concerned about this sort of thing than the typical Walmart customer.