Shipping stuff is pretty cheap, but distributing the supply chain and creating multiple factories making the same product is incredibly expensive.
Let's say you have a hard drive supplier. Now rather than the supplier shipping to 1 factory, there are 5. Freight rates are going to be higher because you have a lower volume. Increased demand on one continent means you need the right balance of material going to that factory rather than simply upping the order for your single factory. Incorrect sales forecasts now mean you have inventory in Europe but need it in the US. You either need to pay to move it, try to get your suppliers to reroute things (always for a fee), or build finished units and ship them to the US, potentially facing higher tariffs than shipping in components [1]. Inventory costs are higher while you figure this all out, and you have increased logistics costs.
You're paying a (bigger) team of people to manage this, and expediting shipments as needed (likely at 3-10x normal cost depending on how expedited, market demand for shipping, etc).
Then there's product consistency. Even if you order identical equipment and keep all the same suppliers, you'll have different issues at each facility. Sharing best practices around the world is challengings and frequently done poorly. [2]
Then you have tariffs and government regulations. If you were 0.25% of GDP for a country, you can go to the government and lobby harder than if you're 0.05% of GDP in 5 different countries. [3]
-- [1] https://hts.usitc.gov/current offers some light trading if you want to find tariffs for the US. They're incredibly detailed, and the smallest difference could change from a 2% tariff to 60%.
https://en.m.wikipedia.org/wiki/Chicken_tax is also interesting.
[2] I know of a distributed manufacturing setup where two "identical" factories have significantly different quality outputs. The best rationale they've come up with is a difference in altitude and climate.
Corporations who have distributed manufacturing like this often have a corporate team who travel between locations checking how well locations are adhering to the company defined best practices.
[3] Definitely don't discount this step! I've worked for 4 manufacturers professionally, and I know for a fact 3 of them have pushed for tariffs and exemptions from regulations. #4 likely did too, but I don't have a specific example in mind. In each case, the difference in profits were 7 or 8 digits long.