The U.S. is a pro when it comes to this because it's the most warmongering country in the world:
Yes, naturally. Getting involved in conflict is related to a country's power and global reach. Countries seek to control the environment around them: securing trade, resources, protecting allies, etc. As a general rule, the more of the world that a country is involved with the more it risks being drawn into conflict, and the more powerful it is, the more it has the ability to intervene militarily.
As a result, just because the USA is the country most involved in conflict, it does not follow that US nonintervention would necessarily result in less conflict, because any vacuum will be filled by other states' power. For instance, Russia could be "given" Ukraine, but it would not stop there. Once Ukraine were secure in its sphere, it would move on to new countries to spread its influence over, by hook or by crook. Without US military deterrent in the Pacific, China would almost certainly aggressively start to assert dominance over the Far East, with its military a key component.
One could even consider that the presence of a supreme global power like the USA may actually
reduce conflict globally, because it forces potential belligerent minnows to consider the ramifications of the supreme power's disapproval. The cost of this is that supreme power has to get its hands dirty instead; of course, it also tends to benefit the supreme power, who can pressurise countries to do things the way that they want.
Ukraine is a sovereign country but it was manipulated by the U.S. as part of the latter's projection of power:
Yes, we supported people to campaign effectively and win a democratic election. How naughty of us! Russia, meanwhile, has been happy to support just stuffing the ballot boxes.
Let's have a look at some of what Russia's been up to in Ukraine:
Explaining the two countries’ intertwined histories, the armed conflicts in Crimea and the Donbas region, and disputes over gas supplies.
www.chathamhouse.org
Over time it has become clear Russia is unwilling to settle its borders with Ukraine and acknowledge its territorial integrity as an independent state.
www.chathamhouse.org
Do you think Russia has a right to subjugate Ukraine, and that the Ukrainian people don't merit rights and self-determination? If the Ukrainians don't merit these, why should the Balts, Poles, Georgians, Kazakhs have them either? Where would Russia stop?
Why would it stop? Would the world be a better place if we just let countries like Russia take what they wanted? Do you just think weak nations should be sacrified and thrown to wolves, just so long as we aren't remotely wolf-like?