The USA have won just one match since Brazil 2014, where they impressed by reaching the round of 16, while that victory is the only one Klinsmann's men have notched in nine games.
A 3-2 defeat away to Chile extended the Americans' current losing streak to three games and Klinsmann argued his players arrived in camp unfit.
With the regular season of the 2014 MLS campaign having finished in October, a significant part of Klinsmann's squad arrived in South America after almost three months off and the 50-year-old was frustrated by their unwillingness to do extra work.
"It's difficult for me now to get them out of vacation. Some of them played their last game in October. In October!" Klinsmann said, according to the official website of the MLS.
"I want to help them get back into shape, get back into rhythm, but, oh, by the way, we're going to play [two friendlies]. So some learned over time and prepared themselves really well, and some don't have that knowledge yet.
"They don't have that 'oh, OK, at the beginning of December, go to Athletes' Performance in Phoenix and get myself fit'. That culture we don't have yet.
"What the other sports are doing really well, they use their preparation for pre-season, four to six weeks prior to going into pre-season with their NBA team, NFL team or whatever, they go to these fitness institutes and they get themselves fit."
Klinsmann added: "But the culture is not there [with my team]. They've got all the material. They should have done that [work] twice a day but reality is still different.
"Reality is, education-wise, we are not there yet, that they [do not] understand, 'Oh, I've got to do this, I've got to do that'. It's a lot to discuss.
"It's fine. It's just where we are right now, and we want to keep improving."
While there has been frustration amongst fans and pundits about the USA's post-World Cup form, Klinsmann seems unfazed.
The USA defeated Ghana and drew with Portugal to reach the round of 16 where Belgium needed extra time to eliminate Klinsmann's team 2-1.
Since the tournament, the USA have defeated Czech Republic; lost to Colombia, Republic of Ireland and Chile; and managed draws with Ecuador and Honduras.
"In many different ways, [the results are] explainable," Klinsmann said.
"The tension drops after the World Cup.
"I think all of the teams go through that but I think the more experienced teams, the teams that have far more peer pressure in their environment, they maybe allow themselves to drop 10 or 20 per cent and not 30 or 50 per cent."
The USA's next match is a friendly against Panama on Sunday at the Los Angeles Galaxy's Stubhub Center.
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