The former AFC Portchester player finished off some nice approach work from Samuel Ndlovu to net a 76th minute decider against Portland at the Victory Stadium.
Ndlovu, formerly of Chichester and Baffins, was making his first competitive start for US on the left side of midfield.
‘It’s amazing how a win can transform your weekend,’ beamed US boss Tom Grice, whose side had not played since a dismal 3-0 home loss to Alton in an FA Cup tie a fortnight earlier.
‘We asked for a reaction and we got exactly what we wanted. Everybody stood up and was counted.
‘It was a fair result. We controlled the first half but let Portland back into it in the second half.
‘We had three one on ones and Joe put one of them away.
‘We were very strong defensively, and we put the ghost of the 3-0 loss to bed.
‘Hopefully people will start taking notice of the fact we’re not going to be pushovers this season.
‘Portland had players with Southern League experience in their side.’
US lined up in a 4-4-2 formation with assistant boss Tom Jeffes and Jack Barker at centre half with Connor Saunders and John Cass at full back.
Ryan Smart and Obi Saidy were central midfield with Ndlovu and Cameron Quirke out wide with Johnson and Brodie Spencer up front.
Johnson has now scored three times in his opening two USP league outings, having lifted the curtain on his season with a double strike in a 3-3 draw at Alton.
Owen Scammell - son of ex-Gosport goal ace Neil - came on for his Wessex Premier debut, while new recruit Wilton Joseph, a forward, was handed his first ever appearance for the club.
Joseph was recommended to US by Navy colleague Shaun Benjamin - a US player in the mid-noughties who has returned to sign on again for 2021/22 - and has international experience in the Caribbean.
Joseph could well be handed a start in Tuesday’s Hampshire Senior Cup trip to Eversley & California.
The north Hampshire club play a step lower than US in the Combined Counties League Division 1’
‘I don’t know anything about them,’ conceded Grice. ‘I will probably take the chance to have a look at some of those who have been on the bench recently, but we’ll be taking a strong squad.’