As I understand it, the house frame, ie. the load bearing part of the house is wooden. The outer brick is just a facade, ie. it gives no structural integrity to the house.
Just as long as they will stand up to our weather, not be built as flimsy as those in Rural America and not turn into shrapnel in a big 10 year gale.
I would hope they are substantially cheaper too. Outside of wealth hotspots the price of houses in America is very low in comparison. This tallys with they lack of employment protections, so mortgages are easier to get if you house costs the equivalent of £40k. If after Brexit the Tories, as expected, go after the employment rights to encourage foreign investment we may be forced to build cheaper so that banks will lend to people with little to no job security.
To put this into perspective (Admittedly i'm not in the US, I'm in Canada but they follow almost identical building codes). For a 2,000ft2 "custom" (i.e not off plan from a new built estate) house you're looking at around $400,000 ($300,000).
Around $100,000 of that will be the earthworks and foundations (digging out and concreting in the basement).*
Around $180,000 of that will be the interior (plasterboarding/plastering, flooring, electrical, plumbing and interior fixture and finish.
Around $20,000 of that will be permits and design costs
Around $40,000 of that will be roofing, windows and exterior (i.e. siding, or rendering)
And around $60,000 of that will be the actual framework for the house, a fair chunk of that (in the region of $5-10k) being floor joists that aren't going to change with wood or brick construction.
The savings probably isn't as much as you think, as only the $60,000 cost is really going to change.
The reason some random home in the midwest could be built for 40k is because labour will be super cheap, the interior will be very basic and the house will probably be a small bungalow on a plot of land miles from anywhere.
*Foundation in this instance would be 8-10ft deep, 8"+ thick poured concrete or concrete blocks. That's for a basement, but anywhere cold the foundation needs to be at least 6-7ft deep so it gets beneath the frost level and doesn't get forced up out of the ground. Same reason all services (water/sewers) are 7' beneath the ground too.