I can only speak to the US side of things.

It's important to remember that the Klan went through several revivals. I use the term revival because they played an important role in the maintenance of the US' Protestant hegemony. The first revival was of course the Reconstruction Klan, which was a sectional and violent articulation of the Klan. The Second Klan--ranging from 1915-1944, but some scholars demurred and end it at 1930 due to leadership issues--officially eschewed violence. When Rev. Simmons revived the Klan, he wanted to push beyond the sectional, violent identity of the Klan and establish a national Klan. Through the help of the Southern Publicity Association, Simmons changed the rhetoric of the Klan. Rather than articulating their white supremacist beliefs as purely racial hatred, they spoke of the love of the white race, especially white women. Though they spoke of love, this was still bald white supremacy that denigrated others. Non-violence was the official position, but klaverns (Klan chapters), particularly in the south, still engaged in violence and terrorism.

However, the Klan was also, but not only, nativist. According to the Klan initiation ritual,

Only native-born, white American citizens, who believe in the tenets of the Christian religion, and who owe no allegiance of any degree or nature to any foreign government or institution, religious or political, or any sect, people, or persons, are eligible for membership. (See, Jackson's Ku Klux Klan in the City)

But it was not this simple. The Klan's negotiation with ideas of what constituted foreign was complex, like other groups that had nativists panks--e.g., The Know Nothings. Rather, the Klan had several auxiliaries that allowed members who could not make it into the Klan itself. One such auxiliary was the Royal Riders of the Red Robe was another auxiliary for foreign-born white Protestants. Persons who were Anglo-Saxon and spoke English were allowed to join this auxiliary. Mostly, it appears that the Klan targeted Canadians to join, but little work is done on Klan auxiliaries (see, Richard, Mark Paul "'Why Don't You Be a Klansman?' Anglo-Canadian Support for the Ku Klux Klan Movement in 1920s New England:". The American Review of Canadian Studies 40.4 [2010]: 508-516) But this is largely the 20s legacy of the Second Klan.

Simmons would lose control of the Klan to Hiram Wesley Evans, who gave up control in 1939. Under the leadership of Evans, the Klan was beginning to lose national influence. Klan members began to leave the organization and sought to form their own hate groups. As the fractioning of the once rather monolithic Klan began, Klansmen attempted to join in solidarity with the Bund, like George Deatherage, to once again reach prominence.

Deatherage left the Klan and revived the Knights of the White Camellia. Deatherage believed that the Nazis borrowed their anti-Jewish sentiments. Deatherage beleived that his members should support the Bund to the point that instead of burning crosses, he advocated that the group should now burn swastikas. But as for remaining members in the organization, the groups were torn on the Bund. Southern Klansfolk in particular disliked the Bund, but Klan leaders in places such as New York, New Jersey, and Michigan supported the Bund, at least according to Bund leadership. For example, in 1940, robbed Klansfolk stood with uniformed Bundsmen in New Jersey. At this meeting, the Deputy Bundesführer addressed the crowd of hate, "When Arthur Bell, your Grant Giant, and Mr. Smyth asked us about using Camp Nordlund for this patriotic meeting, we decided to let them have it because of the common bond between us. The principles of the Bund and the principles of the Klan are the same." In a sign of solidarity, a Klan leader then joined hands with a bundsman. And then there was a Klan wedding beneath a fiery cross.

But not everyone was in favor of this meeting. Once news got out of the camp meeting, the meeting was rebuked. Klan leaders in New Jersey distanced themselves from the meeting. Two members of the NJ Klan’s leadership were kicked out of the group for their role in the meeting; including the one who joined hands with a bundsman. Official Klan papers increasingly criticized the Bund. (See, Chalmers' Hooded Americanism.)

An anti-US German propaganda poster
The German poster is used to paint the US as a racist warmachine using the KKK as a focal point of the image. I don't know much else about popular opinion in Germany of the KKK at the time but it seems that it was largely negative.

There is nothing written anywhere to suggest Germany tried to reach out to anyone in the KKK during WWII. The KKK during this time period was already on the decline after the Great Depression so there really wouldn't have been much incentive for the Third Reich to try to reach out to them.

James Colescott did try to build positive relations with the German American Bund, which was a pro-nazi German American group. This move however only helped to further splinter an already fractured KKK so it was not a very popular opinion within the klan.

The KKK remained dormant after that until the Civil Rights Movement gained momentum after WWII, and people like Samuel Green used the opportunity to revitalize the KKK.

Did they condemn or support the Holocaust?