American groceries in Tokyo?

We're in Japan for a couple of weeks and our young kid is super mega-picky about some food. There's plenty of stuff around that he does like, like udon, ramen, and teriyakai chicken, but it would be helpful to get some of the kinds of foods he's used to eating.

So I was wondering what the prospects are for finding some typical American groceries in Tokyo? (We'll be staying in places with small kitchens so we do food prep.)

Things I'm hoping I can find in most supermarkets, but would love confirmation:

• Italian-style dried pasta and tomato sauce.

Things I'm unsure about – are these staples in Japan?

• Peanut butter.
• Fruit jams
• Butter

Things I'm assuming I'll need to hit an international market for, and even there might need some luck:

• boxed Kraft mac & cheese
• American-style breakfast cereals

Any tips/pointers appreciated. We're obviously hoping to broaden his palate as much as possible, but we'd feel better with some fallback options.

Edit: while in Tokyo we’re staying in Asakusa but I’d be okay traveling to another neighborhood.