Watch: The BBC's Shaimaa Khalil is in Arizona to hear from residents about the expansion of data centres. A year ago, a longtime US senator was not thinking much about data centres. Now, according to one of his advisers, he is having regular meetings with staff to track their impact and working on new legislation aimed at curbing their rapid expansion across the country.

“

"This happens sometimes, something starts slow and then it goes fast," the senior policy adviser to the Democratic senator told the BBC. The person spoke on condition of anonymity as they are not permitted to speak to the press.

The 180-degree turn in this senator's attention was driven almost entirely by a growing wave of public backlash that has seen politicians across the country scramble to keep up. Public sentiment has turned against the expansion of data centres, the large warehouses that store processing power needed for internet activity. Packed with rows and rows of computer chips, sometimes seven-feet high, data centres have turned into more than infrastructure for the internet. They are now the physical embodiment of the recent and explosive growth of artificial intelligence (AI) technology, and the varied fears people associate with it.

“

"I don't want to be the guinea pig for this," Indiana resident Angelita Soriano told the BBC. A backlash over data centres is another threat to the AI juggernaut.

A new Amazon data centre is being built directly across the street from her home. When complete, the 26-building structure will take up more than a square mile in her neighbourhood and maintain 782 diesel-powered generators. Some data centres are even larger. In Ohio, a joint effort between OpenAI, Nvidia, SB Energy, and the US Department of Energy is set to build a data centre complex that will stretch for roughly six square miles, the same size as most townships in the US.

There are about 3,000 data centres currently operating in the US, with that number potentially doubling in the next few years, according to a report by the Pew Research Center. Data centres are built through very local rules and permits, meaning federal lawmakers like US senators have little say in the process. Yet, opposition has become so strong so quickly in the US that suddenly, politicians at all levels are now all but required to take a stand.

“

"This isn't just an issue on the left, there is huge pushback among conservatives to data centres," Chloe Autio, an AI policy adviser, said. "Whoever articulates a clear position and sticks to it, in either party, really stands to benefit."

Her analysis was echoed by the adviser to the US senator working on data centre legislation.

“

"There is a clear policy need here that we're looking to fill," he said. "This is a major backlash across the country - constituents are seeing the impacts of data centres and they do not like them."

That has put many on Capitol Hill - even Republicans - in direct conflict with President Donald Trump, who has championed the unrestrained growth of AI technology. Trump has dubbed the backlash to data centres a "sick conspiracy" and said people and towns working to keep the buildings out are "backwards and poor". His ire has been used as a boon to Democratic politicians looking to draw midterm votes from unhappy or undecided constituents.

The BBC spoke to residents of Indiana, Arizona, Michigan, Pennsylvania, and Oregon, all of whom have been organising locally against the development of data centres. They expressed concerns about many aspects of the buildings, including their size, construction and operational noise, their impact on air, water and energy resources, as well as the speed at which they seem to be approved by local authorities.