That's one if the main issues that gets on my nerves about the UN, the US is the only nation in the UN with a military that can hold it's own and other nations come to us first expecting us to send our people and resources when they're incapable of protecting themselves. Yet even knowing this they make little to no effort to improve their own fighting forces. Regardless of what conflicts arise across the world, if Russia or China is involved the US is the only nation capable of getting involved to maintain balance. Don't get me wrong there are always Americans willing to put their lives on the line to help those in need but it's ridiculous for the rest of the UN to automatically assume that it is our job or responsibility. We're like the big brother that is always having to save the little brothers from fights because they never took the time to learn how to fight on their own, eventually everyone needs to learn how to take care of themselves because it's a fact of human nature that the peaceful societies most of us live in are anomalies when it comes to human nature. There is always going to be someone willing to kill you to take what they want and if you're not prepared to take care of yourself you only have 2 options, beg for help/mercy or die.
You seem to misunderstand something, America is very powerful, by FAR the most powerful military right now and they benefit from other countries coming to them asking for aid in such situations, you only need to look at the three main regions of US military activity over the world :
USA competes with Russia in Ukraine and has NATO members bordering Russia.
USA competes with China in the South China Sea and has many allies surrounding China (Taiwan, Japan, South Korea, Philippienes)
USA competes with Iran in the Middle East and has allies there (Saudi Arabia, Isreal...etc)
The USA also has major military presence in these regions, either as military bases or Fleets :
America wouldn't want any of these countries to stand up on their own two legs and become "independant", why ? Because America's influence will start to fade in that case, Europeans before the war got into the habit of acting really cocky and trashing America until this war came around, then it became clear why European states are still America's vassal states, they cannot protect themselves without America, exactly how America likes it.
It is kind of funny that the strongest military in the EU is probably Greece, mainly because of grievances with another NATO member, Turkey.