I love to look at WW2 photos, particularly with an eye to items I'd like to model, I have noticed that US forces in the ETO used a number of German-style gas cans. I say "German-style" because the British made an almost direct copy of the German 20-liter fuel can. The original Britsih 4 gal. "flimsies" lived up to their nickname. The Brits were suitably impressed with the Wehrmacht 20-liter can, and rather than reinvent the wheel, they adopted the design as a 5-gallon can. When the US adopted the idea for a 5 gallon fuel/water can the general layout was kept but the cans were modified for US production. The US water can has a totally different flip-top lid and a brown enamel lining, whereas the fuel can has a screw top closure and no lining. In all the years that I've been modelling, I've only run into one good model of the WW2 US type water can - the resin offerings in 1/35th by Armando Bayardi.
Model trivia - Historex made 1/32nd styrene kits of fuel cans for the Squadron Shop back in the 1970s. These were supposed to be mixed "US" and "German" styles. However the "German: cans are actually modelled after the British production. Cast into each one is the "WD" and the British War Dept vertical arrow.
Anyway, your model can be carrying US, British, or German cans (at least in Europe), just don't have the German or British cans on a USMC vehicle in the Pacific!
Gary