After the brilliance against Australia the week before, England had to come back from 8-6 down to grind out a 26-13 result which owed more to hard work and pragmatism than creativity.
Yet while Johnson admitted his team lacked cohesion, he was happy with the composure they demonstrated against feisty and physical opponents.
Johnson said: "I got asked: 'Oh haven't you got to win in style?' These people don't understand what you are dealing with.
"It's bloody competitive, bloody tough. They were strong in the breakdown, a couple of times up the middle of the field I wasn't comfortable in my seat. These guys can play. How many times do they have to do what they can do before people understand that?"
Despite domination in the scrums and enjoying the majority of possession, England struggled to control a match in which they led 6-3 at half-time before going behind immediately after the restart when Samoa full-back Paul Williams went over to record the first try scored by his nation in a senior international at Twickenham.
It was also one of those days when England appeared destined not to score a try, having three rightly disallowed when Ben Foden failed to get the ball down before being swept into touch, when Chris Ashton raced between the posts only to be brought back for a forward pass and when Mark Cueto stepped into touch before releasing the final pass.
"We couldn't buy a try at one point," said Johnson.
"I wouldn't have complained if we had been brilliant throughout but life is not always what you want. I was frustrated but we had to keep our composure and find a way to win it.
"Going behind just after half-time wasn't great but in hindsight it didn't kill us.
"They chanced their arm a bit. It's not great when they come out with the ball on your 22 right under the posts. But Toby Flood and Ben Youngs handled the game pretty well.
"They were very composed at half-time. We had to build our way back into the game which we did and ultimately got ourselves well ahead."
They did so with second-half tries from centre Matt Banahan, making his first Test start at outside centre, and replacement flanker Tom Croft, and Flood added 16 points with the boot.
Even so, there were a few anxious moments in the last 10 minutes when Samoa appeared at last to wrest the initiative at the scrummage and Fautua Otto dived over to reduce the arrears with the penultimate play of the match.
For Johnson, however, the bottom line was that England found a way to win to consolidate their progress this autumn, which has included a narrow defeat by New Zealand as well as that heady win against Australia.
Johnson said: "All these games are winnable and loseable, no matter what you have done the week before.
"Samoa were strong in the tackle. They put a lot of bodies in the breakdown, made that ball slow. We weren't as cohesive as we have been.
But we showed composure, the players understood what was going on and tried to fix it. The whole crowd was getting edgy, the scoreboard was too close for comfort and you have to deal with it. And we did okay. We let them get out of the corner a bit too easily. But we kept getting at them and we got there in the end."
There was an air of disappointment in the England dressing room that they had been unable to deliver another show for the 70,000 fans.
But with the physical challenge of South Africa to come on Saturday, Johnson said: "Some of the players were a little bit glum afterwards but that's what Test match rugby is, you find a way to win."
England's new outside centre Banahan believes he silenced his critics after scoring one try and creating another.
Banahan started alongside Bath club-mate and room-mate Shontayne Hape in a new-look centre pairing after winning his previous five England caps on the wing. At 6ft 7in and nearly 18st, Banahan offers a powerful ball-carrying option but England are also confident he has the handling skills to bring others into play.
Banahan scored England's first try after a move involving Hape and Chris Ashton.
For Croft's try, Banahan claimed the interception and he then flicked an offload out the back of his hand to former Leeds No 9 Danny Care.
"I'd like to ask them (the critics) and see if they have got any more doubts," said Banahan. "I have always got confidence in myself and the coaches have confidence in me, that is why they play me there. Now I would like to see if those people still doubt me.
"If they don't think I can play 13 that is their opinion but I did my best and, hopefully, I did enough after that first 15 minutes of shaky time.
"The Bath coaches said to me 'you've got the skills, go and prove it' and for the last four weeks with England I have been running at 13 and getting my lines."
Former Bradford Bulls rugby league star Hape, the official man of the match, is becoming an increasingly influential figure in England's midfield.
"I thought Shontayne was brilliant today. I think he's getting all the praise for that try but I called that moved," said Banahan.
Leeds Carnegie's Hendre Fourie played a full 80 minutes on his first start for England, to win his third cap.
England: Foden, Ashton (Armitage 75), Banahan, Hape (Hodgson 75), Cueto, Flood, Youngs (Care 68); Sheridan, Hartley (Thompson 56), Wilson (Cole 56), Lawes (Attwood 68), Palmer, Haskell (Croft 68), Fourie, Easter.
Samoa: P Williams, Lemi (Otto 60), Pisi (G Williams 76), Mapusua, A. Tuilagi, Lavea, Fotualii, Taulafo, Schwalger (Paulo 48), A Perenise, A Perenise (Johnston 68), Levi (Poluleuligaga 67), Thompson (Tekori 41), Treviranus, Salavea, Stowers (Aiono 66).
Referee: P Fitzgibbon (Ireland).