Had the same problem with mushy rice when I moved from Asia to the UK for uni and had to buy "british-style" long grain rice from Tesco and other supermarkets. Fixed it by washing the rice a LOT - like up to 10 times until the water was actually clear.

(Back home we wash rice only 2 times and all the surface starch is washed off. My theory is that rice I ate at home is vacuum packed while the other rice bags aren't, so maybe the grains rub together more during transit and result in more small starch dust??)

Also don't worry about the water cup measurements, just do it the Asian way: Fill pot evenly with rice, put tip of index finger on the surface of the rice layer and fill with water to the first knuckle of your finger.

How to proceed to make basic east Asian style plain white rice:

• NO salt (Add light soy sauce and/or sesame oil after rice is cooked for fragrance. Also the plain rice is meant to be the "carrier" for the meat/veg. I personally love the taste of rice on its own so my heart hurts a little when my British schoolmates put salt in what they call "plain" rice. Obviously salt it if you're making fried rice etc.)
• Put pot with rice & water on stove, set to highest temp until it just starts to boil.
• Turn stove down to lowest possible heat/fire, cover with lid and leave it for 15ish minutes. I also prefer harder/drier rice so I pop the lid diagonally a tiny bit to let more steam out.
• After time is up, take off lid and let the rice chill for a bit, like 5 - 10 minutes. DON'T serve immediately as from my experience it'll still be a bit mushy.
• Add soy sauce and/or sesame oil here, mix in and fluff the rice with spatula or fork. Leave for a little while more (I just dish out the other things I'm eating or set the table with the rice during this time.)
• Enjoy, eat way too much carbs, go into food coma.

Maybe I'm biased cos I'm Asian and have eaten plain rice every day of my life but if the rice is cooked properly and is nice and fluffy, I won't need to add any extra seasoning, even sesame oil.