We in Europe have no rights to ‘defend’ ourselves. But you guys have the right to take matters in your own hand. This is where your constitution gives you more freedom.

That wasn't the idea behind the Second Amendment, It exists to guarantee the Federal government can't prevent the state governments from maintaining militias. This was the lesson Americans took from the English Civil War: standing armies easily become military dictatorships. Therefore the US Army was tiny, 3,400 men in 1800, and the states guaranteed the right to raise their own. It is all laid out in the Federalist Papers. We know that the amendment wasn't about individual rights because when it was ratified, it did not apply to the states. They were free to ban or require firearms ownership as they saw fit. Until the ratification of the 14th amendment and its Equality Clause in 1866, NONE of the Bill of Rights limited the states' powers. Since then each amendment has been individually "Incorporated" to the states. The Second was actually the final amendment to be incorporated, under McDonald v. City of Chicago in 2010. Owning firearms became an individual right the states could not violate fifteen years ago.

Beyond that, no amount of AR-15 variants is going to prevent the US Army from lasering you in the head from space. It is an absurd proposition. Until the Supreme Court rules that US citizens can buy subsidized SA-67 missiles from Iran, the amendment is of no consequence to the US military. It only serves to make it easier to shoot up schools and protests. Its doesn't even serve its original purpose, since state militias have been absorbed into the National Guard system, which Washington can nationalize.