If you intend to stay in Europe then you will need an EASA Part 66 B2 licence to certify avionic systems on civil aircraft.
The information can be obtained from the EASA web site, look for Part 147 (training) and Part 66 (licence) sections. In the UK the two main training organisations are City of Bristol or Kingston University, don't know of any training organisations where you are located.
The FAA A&P is still very usefull in Europe, and you may have more assistance in the US training establishments with the GI Bill.
BR om15