USB devices are block devices like any other. Linux doesn't care if you install or boot from a SATA disk or a USB disk, it makes no differences in that regard. The only niggle is can be BIOS support, ...
I've just picked up a new laptop, and I have to say at first glance, it looks like a real beauty. It's an HP 15-bs166nz, which I got at one of the large electronic chains here in Switzerland for CHF ...