27kg (around 60 lbs) is an awfully heavy pack for any average sized person. As a rule, you should try not to carry more than 25% of your body weight on a long hiking trip, especially over steep terrain. So for an average guy at 160 lbs of wieght, he should not carry much more than 40 lbs. There is not a lot you can do to reduce food weight -- once you are using freeze-dried food that is about as light as you can get, so you need to reduce weight in other areas. One is to carry a water filter so that you don't have to carry more than a liter on you at any time (of course, this does not apply if you are in the desert -- you may have to carry a 3 or more liters per day in really hot desert areas with no natural water.) Another way is to reduce the weight of your tent and sleeping gear. You can buy spacious weather-resistant tents that are around 4 lbs (versus an average 8 or 10 for a mid-priced 2-man tent) but they are costly. Sleeping bags can be light depending on the minimum temperature you expect to encounter sleeping. You need to consider the actual weight of every item you have, from your boots to your hat -- the ounces (or grams) all add up.
I'm curious, though: are you planning to do extended multi-day hikes (like 100s of km) through remote wilderness areas? Most through-trails, even in the National Parks (except for Alaska) come to within reasonable distance of developed places where you can re-supply every few days or so. The US may look wild on a map to a European but we aren't Siberia. There are settlements and cross-roads shops everywhere. America is full of cheap food.
That is what most people do, carry food and supplies for 4 days to a week and then get more at a shop somewhere near the wilderness area (or stored in their car) before venturing back out into the wilds. At 20 ounces per day of freeze dried food, even a week's worth would be under 10 lbs. Add another 10 for water and other lunch food (dried fruit, biscuits, cheese, tinned fish, etc.) and you are still only at 20 lbs. for food. You could add another 5 to 10 lbs of food, which would make your pack heavier at first BUT as you hike each day you will eat 1 1/2 pounds or so and your pack will get lighter. With a 5 lb tent, 4 lbs for a sleeping pad and bag, one lb for a compact stove, you would still have room for 10 lbs worth of clothes, tools, cookware, etc. and be at or under an average of 40 lbs. on your back for the trip.
I don't think food is your biggest weight concern.
By the way, I read your profile. You do know that Chris mcCandless did not know what he was doing and that he died as a result of it? I hope you are not using him as a role model. Also, you can't walk from Boise, Idaho "into the wild" and live there permanently, in Idaho or in any other state in the USA except for Alaska. All property is either privately owned or under the management of the government and there are restrictions on staying on it -- you are required to register to use trails and camp in almost all areas and would not be permitted to do so for months at a time. Winters are more severe in many ways in Idaho and Alaska than in Sweden.
Your questions about food and packing indicate you are relatively inexperienced at wilderness camping and packing. I don't know that as a temporary visitor you would be permitted to own and carry a gun or to remain in the US without a permanent address.
I hate to discourage someone's dream, but I would caution you to use common sense and not be overly optimistic about a fantasy of "living off the land". Read "Into the Wild" again. He died a horrible death of poisoning and starvation because of a few really stupid mistakes and lack of experience. Is that what you want to do?
