That wont work coz I need to give a mobile number to send SMS and to activate the market
I live in Germany but I could set up an US Microsoft Account for my Lumia 920 no problem.
I didn't have to provide any mobile number and for the free apps I didn't even had to provide an US address.
But maybe it worked so hassle free for me because I set up my US account on my computer first (which is routed through an US based VPN connection) and then just logged in on the phone (which [for now] still has a German IP address since WP8 unfortunately doesn't support VPN yet) using that account I did set up before.
I even managed to add my German Visa card to my US Microsoft account so that I can now even buy payed apps in the US store no problem - that was a little bit more tricky though. If you're interested in how this can be done let me know but it might be a little risky since it involves entering an "incorrect" postal address and I can't take any responsibility of course.
Today I figured out that I can even download apps from the German store with my US account by just chancing the "Country/Region" in "language+regions" settings to Germany. I downloaded several apps this morning and they sill work after changing the country back to "United States". Haven't tried if I could buy payed apps from the German store so far though.