Hardware development is just extremely difficult. The smallest company that I'm aware of that has their own laptop design is Framework, but their laptops are also about twice as expensive as equivalent models from other brands.
In addition, since basically all modern computer manufacturing has to go through Taiwan due to TSMC's near-monopoly on competitive semiconductors, it makes sense to outsource design to Taiwan too. They already have the industry for it, and there's no reason to have a random American company add their own profit margin to the price for no reason.