Can I take food with me?

I am traveling to Japan from the USA. Can I take sealed foods, such as tuna or beef jerky?

To bring any kind of meat in Japan you will need to have the appropriate government department in the States inspect it and certify it safe to bring to Japan. Some souvenir stores aimed at Japanese people may sell pre-inspected beef jerky if you can find them. Several times in the last few years imports of US beef have been completely banned in Japan, so it is possible you won't be able to. If you tried to bring it in without declaring and it was found (there are sniffer dogs) you could face a fine.

Incidentally canned tuna is very widely available here, so kind of an odd thing to bring to Japan.

Generally for island countries like Japan it is illegal to bring in any meat, fruit or vegetables, in order to protect the country's biosecurity.

I would not bother with any meat products, depending on the rules at the time & the inspector, they may be confiscated. As the other person noted, canned tuna & other fish (I love the saury) is readily availible and cheap. No fresh fruits or vegetables either, they will get confiscated.
We normally bring other food products over for my wifes family. These include things such as bagels, pancake mix & syrup, fried pork rinds (for Otoosan), candy, etc.. Most dry goods & canned products are OK as long as it is not meat products.