Q&A: Does God’s promise to Joshua and Israel in Joshua 1:9 apply to us?

By ‘us’ I’m assuming you mean the Jewish people, and specifically those living in Israel today.

You can’t cherry-pick God’s promises. Even if you accept those verses at face value, the promise is contingent upon the nation remaining faithful to God’s commandments. In the Book of Deuteronomy (chap. 28), God warns Moses:

Q&A: Does the Bible state that the original land of Israel extended into Iraq and Egypt?

Source: http://www.israel-a-history-of.com

Actually, no. The Book of Deuteronomy is very explicit on the issue, with the expression avor et-hayarden el-ha’aretz asher Adonai eloheinu noten (‘pass the [River] Jordan to the land which the Lord our God has given’) repeated (in various permutations) a dozen times (2:29 / 3:27 / 4:21, 23, 26 / 9:1 / 11:31 / 12:10 / 27:2,4, 12 / 30:18).