Unfortunately as it was a political decision to remove the UK CAA from EASA and not make sure there was an agreement in place for converting UK to EASA licences, we need to petition the UK Government to try and get it rectified, hence you need to be a UK citizen or resident. Having an FAA licence would not entitle me to use a US Government system to petition them if I wasn't a resident or citizen. UK licence holders who aren't UK citizens or residents could encourage those who are to petition, or petition in other ways, if they felt inclined.