Is there a legal way to get a US App Store account from outside the US?
I'm not sure if using a fake address would be legal. 

Technically, you can create an account in the US Store using an iTunes Gift Card and a fake address/phone number. You can buy iTunes Gift Cards in eBay (some sellers will expedite things by sending activation codes by email).

If you're only interested in free Apps, you can create an account without the Gift card. There is an Apple support document describing the process. 

Regardless of payment, Apple asks for a valid US address to establish an account, so the legality of this depends on where you live.