Address post cards to overseas from Japan

My question is about how to fill out the mailing address for post cards sent from Japan to back home (USA).

I will be in Japan for 2 weeks soon. Usually when I travel overseas, I like to bring along the addresses of my friends pre-printed on peel-off mailing labels. I buy a post card in a shop, find a stamp, stick their mailing address on it, and drop in a postal mailbox.

What is the proper way to address a post card sent from Japan to someone in the USA?

I do not speak or write Japanese. If I simply use roman (English) characters, will that be OK? The typical format I use is:

Name
Street Address
City, State, Postal Code
USA
米国

If I simply add 米国 after the last line, is this correct and appropriate?

By the way, can anyone tell me the cost of a postage stamp to send a standard size post card from Japan to USA? About how many days should I expect it will take to arrive? Finally, is it OK to just put a stamp on the card and drop it in any postal mailbox?

Thank you!

Yes, the address is fine. Postage fee for postcards is 70 yen, they will arrive in about 5-7 working days.

POST CARD(write or print clearly)
Name
Street Address
City, State, Postal Code
USA(write or print clearly)

No need to print 米国(you can do so if you want).

Post cards sending cost you 70 Yen(fixed International postage). 70 Yen stamps are no longer on sale, so you need to buy 2*30 Yen stamps and 1*10 Yen stamp at post office. Combini stores only have 10, 52, and 82 Yen stamps.

You can also just go to the nearest post office (search "post office" in Google Maps, it really has all of them) and show them your postcards, they will know what to do. At a small post office in the middle of a weekday, you are almost guaranteed no wait time.