Use a US-based proxy to sign up (to get past the geolocation) and give them the US number when they ask for your cell number. Then you'll get your own US number from GV and can drop the other one. You also won't need to use a proxy after signup. After that, you can use it for free US-based SMS and voicemail.
Well, the US proxy thing I was contemplating about myself. The OP seems to imply that all you need is US phone number, no proxy or anything.
(I'm the OP) Yes, but I also needed a US number to get started. The reason I didn't mention a proxy is because that's super easy, and I figured it was too obvious to mention (although I should have said that you only need to use the proxy for about 5 minutes while signing up). Getting a US number to get started is the hard(er) part.