Are the following japanese phrase correct?

アメリカの広さは、日本の二十六倍くらいです。
The size of the US is about 26 times larger than Japan.
アメリカの国土は、日本の約二十六倍です。
The US　territory is about 26 times larger than Japan.
アメリカは、日本より二十六倍くらい大きいです。
The US is about 26 times larger than Japan.

アメリカは、日本より2．6倍くらい人口が多いです。
The US has about 2.6 times larger population than Japan.
アメリカの人口は、日本の2．6倍くらいです。
The population of the US is about 2.6 times larger than Japan.

日本は島が多いですが、アメリカは平らな土地が多いです。
Japan has many islands but the US has many flat land.
日本は島国であるのに対し、アメリカは平地が多いです。
Japan is an island nation while the US has many flat land.

----ikutsuka = some, countless, few, a pair of . no longer many. no longer basically for small products. ex. ikutsuka no tatemono = a pair of bldgs nankoka is for the small products. ex. nankoka no ishi = some stones ----no longer uttate = utatte ----nandaika = some, countless, few, a pair of . no longer many. ex. nandaika no sentakuki = some washing machines nandaika no kuruma = countless autos ----sorera = sore (it, that) + ra (the plural form) = those i desire your textual content cloth's ex to practice you... ----nantooka you may desire to write down nantouka. yet pronunciation is nantooka.

i notice a few grammatical errors, but i cannot correct them as i am still not entirely certain as to what you are trying to say.