Oh, there is more than just one. Not sure where you heard that, but it is very wrong. There are well over 100 of them in the US, including such companies as IBM, Intel, Texas Instruments (which has over 50 alone), Micron, and others. We have one right in the town I live in, and there are around a dozen around Portland alone. Intel has 4 fabrication plants in Hillsboro, Oregon alone, and employs over 1/5 of the city.
Somebody is full of crap and should not be believed if they are trying to say there is only one manufacturer if integrated circuits in the US. Just a simple check of Wikipedia will show that is crap.
en.wikipedia.org
Sort by plant location, if done in reverse, all the plants in the US will be located at the top.
Also, a lot of the chips "made" in other countries are actually designed and patented by US companies. They either pay us a royalty, or they are simply making them for our companies.
Then you do have some companies, like Zhaoxin, in China. They are the largest "domestic" chip maker in China, and make most of the Chinese market X86 processors. But do not try to find one in a local computer store. They use the designs made by Via, originally a US company but moved to Taiwan in 1992. Once a big name in computer chips, now they are largely forgotten. Now they make very budget processors, their 2021 releases are largely equivalent to a budget Intel mobile processor of 12 years ago.
Now I am not a fan at all of Linus Tech Tips, but they were one of the few I found that actually reviewed one of their latest processors.
And their synopsis was basically "It sucks, it's slow, and it's expensive".