Hi,
First what you describe and what the website you indicate are 2 different things:
- you describe a server hosted somewhere where clients remotely connect, and then from that server they use the Internet (over 1,2,3.... IPs)
- the websites offer a software to be installed on the client computer, that allow it to use the 40-50 IPs all over US
The first is done by using a service provider that can give you a server with multiple IPs with different GeoIPs (for example i use OVH and can have IPs all over Europe). The users remotely connect on this server (or more) and use the internet from that server.
The second/websites is more a proxy/vpn solution. I'll done by having a residential DSL contract in all those locations (or a person that allow you to use his DSL connection). Then in each location is a computer (or just software on the existing computer) witch act as proxy for others traffic. On the client side i'll put a vpn software that connects to one of the 40-50 locations and use that remote location as transit. This way a EU client seems to be in US, and watch Netflix :)
I've done all of them, at a smaller scale and in the EU. It's not complicated, just it must be well scaled.
As for me i'm a network engineer for 15 years worked and working on the ISP side, land and mobile networks.
Cheers,
Ciprian