1)if i complete 1500 hours in here , can I apply for those companies in US without an FAA ( I have EASA and JAA)?
Most of the top level US airlines (American, United, FedEx, etc.) require a FAA ATP. Delta says they will accept a FAA commercial
3) if US companies don't accept me without a FAA license , how long does it take to convert my licenses to FAA?
There is no direct conversion of foreign licenses to FAA certificates except for Transport Canada licenses. So you would have to complete a Certificate Training Program (one week), passed the written test (a few days of studying for a foreign ATP holder) and pass the checkride. Your foreign types would not carry over. If you were to do the checkride in an aircraft that requires a type there is an additional requirement to complete an approved ground school and flight training program.