Can I write letters if I’m not a US citizen?

Here’s the relevant sentence from our Terms of Use.

If you are not a US citizen or permanent resident, you may not use the Site or any Content for any purpose in violation of the Federal Election Campaign Act’s prohibition on foreign national contributions and expenditures.

In practice this means that volunteering your time and effort to help write letters is fine, perhaps with a partner or group, but if you’re not a US citizen or permanent resident, you must not spend any money (for instance, on stamps, supplies, and printing costs) on your Vote Forward efforts.