oh god the mythology surrounding samurai, ninja, and their weapons...
For example ninja did NOT wear the iconic garb we think of, that is the outfit of a kaubuki stagehand, meant to symbolize "this guy doesn't exist in the story, he's just moving props, ignore him" so when one pulls a knife and stabs sombody on stage for an assassination scene, people go "ooohhhh he was a ninja!" and westerners visiting japan not knowing what the was going on, go "That must be what ninja wear..." pass it down the cultural line a bunch of times, and boom, you have ninja from the 70's-80's-90's all wearing the same gear.
Whoever posted that second one you quoted glyph... should be pimpslapped with a history book.
Mideval europe never conquered japan becuase japan was on the other side of asia... but mideval knights at their height were in par with the samurai, (Knights reaching their zenith during the hundred years war, and the samurai during the late Sengoku period) both were well trained highly diciplined spiritual fudal warriors and masters of horse & sword. Their choice of weapons and fighting style varied because their battlefields were diffrent.
For example japan has far less access to iron than let's say france (the heart of knightly ways before longbows and guns did that style in) did, less iron means less steel, and less steel means a warrior's sword must be of far higher quality, and the smith entrusted with making it must be a master of the craft, otherwise it's a waste. At the same time a smaller and more rugged landmass yields a diffrent style of combat than say the open planes of france, the forests of germany, or the rolling hills of spain.
Another example is that European knights prefered to survive rather than kill, and all western styles since greece reflected this mindset. this is why all western armies made heavy use of shields. This is somthing that would have seemed cowardly and confusing to a samurai. But in a battle based on equipment, this gives the knight a distinct advantage in close quarters, japanse swords, which kitana exemplifies were insanely sharp, but became brittle as part of the refolding process. Yet knights didn't wield ranged weapons on the battlefield (a fact the english took full advantage of during agincourt) and samurai saw the use of the bow in war as a noble endevor...
Both men were mobile fighters, with well made armor (again we are talking Knight and Samurai at their height, which means custom fit armors and all that.) and while their more exotic weapons would have seemed strange and impractical (Flail & kusrigama) their weapons shared a number of similarities, great swords & katanas, halbard & naginato, Mace (1hand + shield) & Kunabo (2 hands), ans so on.
But at the same time, many of the combat martial arts of east and west are nearly identical. Most europeans stopped practicing how to take down an armored foe and use his weight against him after the gun, crossbow, and longbow, became a great equalizer among men.
Age of Sail Europeans regarded japan as another eastern culture, worthwhile, but with little in the way of resources that they couldn't get from the chinese anyway. Japan's rulers were openly hostile following it's isololation, but content to sit in their little corner of the globe. France, England, ect. had better, far more profitable ventures in The New World, the Asian mainland, and Africa rather than try to crack open an obviously hostile government with few valuable resources. The Dutch had an exculsive trade partnership with japan, even during it's isolation, so they remained "dutch trade turf" so to speak.
Part of the reason the US cracked japan open was to find an asian trade partner that wasn't in europe's pocket.