Psalm 145 speaks to the comprehensive nature of God. God is good to all, faithful to all His promises, loving, near and watchful over all He has made. He upholds all who fall, and lifts up all who are bowed down.
Psalm 146 continues this description noting that the Lord even watches over the alien, one who is not a part of Israel.
It is true, in both Testaments, that God has a particular affinity for those who constitute His people. The promises of God belong to them. But that doesn’t mean that God doesn’t care for anyone else. He cares for all His creation. If He does so, can we do any less?
It is precisely because God shows this care for His creation that the reader is urged to praise the Lord. In fact, beginning with Psalm 146, the rest of the chapters all end with the same phrase: “Praise the Lord.”