Europe reaping what it has sown.
Europe loves to start wars, and then act as if it's the United States that should jump in and do the fighting.
This is such a nonfactual statement. In what European conflict after 1900 has "Europe" started a war against a non-European foe? Excluding the Russo-Japanese War, in which we did not participate except as a peacemaker, such a condition has not happened. Therefore, I assume you are trying to say Europeans start wars among themselves in order to see with which powers the US allied itself? You do see how that makes no sense?
So, if I may make a second assumption, you must be talking about both WWI and WWII? We did eventually participate in both those wars, but it was because it was in our national interests to do so - it was never about altruism. One could even make the argument we entered when we did in both cases (late) to minimize our cost and maximize the benefits of victory.
To give some idea of how much Europe suffered in those wars, Britain endured 384,000 military deaths and 70,000 civilian deaths, or about 1% of a population of 47 million. The US suffered 418,000 deaths, the vast majority of whom were military representing only 0.3% of our population. Moreover, Around 150,000 of those US deaths occurred in the Pacific against Japan. British losses actually exceeded ours slightly in Europe (the UK also fought the Japanese alongside the US). Thus, Britain was hardly sitting around letting the US do the fighting. US losses in the First World War were far less proportionately to the UK and France.
I guess I won't include the either the Central Powers of WWI or Axis Powers of WWII, but they were European nations as well and had horrific losses compared to the US.
By the way, it is still in our national interests, particularly economic ones, that Europe remain a friendly market for goods and services moving in both directions. Hence, the enduring value of NATO - a treaty organization this nation created.
