The only publications they are likely to read regularly are the U.S. Flying and U.S. AOPA magazines because these are informative for the kind of flying these people do.
But not informative on flying in Europe. If you fly in the US join AOPA US, if you fly in the UK join AOPA UK, if you do both join both. People shouldnt expect AOPA US membership to inform them of developments in Europe or to act on their behalf with EASA or the EU.
Guidance on how the scheme will operate and the definition of what is subject to tax is
here.