Why US low mercury fluorescent lamps (Ie. Philips ALTO, Sylvania Ecologic and GE Ecolux) becomes mercury starved and have less initial brightness, while the european low mercury fluorescent lamps (Ie. Osram Lumilux and Philips Master TL-x) pass all their lives without mercury starvation and have full initial brightness?

US low mercury lamps have a much lower dosing of mercury than the EU spec lamps, such that you can often get US made lamps that are advertised as "Low Mercury" with a label stating " NOT for sale in the USA" as the mercury content is above the allowed EPA levels. These lamps are very good life wise, much better than the available lamps in the USA, but they cannot legally be offered there, just made there. The European and Indonesian lamps are very good AFAIK and give a good life, although the mainland Chr@p is incredibly variable from batch to batch.

I don't think you cannot sell 1.8mg fluorescents in US, you only should not mark them as "low mercury"...

Yes, there are still a choice of lamps besides the "low mercury" ones (Alto, Ecolux, etc).   I have had terrible luck with the Alto 8' lamps, so I always specify that I want the standard, non Alto Philips versions and have had no problems with them starving out of mercury or prematurely failing.