I urge that supplications, prayers, intercessions, and thanksgivings be made for everyone, for kings and all who are in high positions..." 

Generally St. Paul's encouragement to offer prayer for those in authority is understood to be a prayer of intercession (often for good reason).   Of course, we have no problem giving thanks for Jesus and his work of salvation (mentioned later in the passage). 

However, the context of Thanksgiving causes us to consider offering prayers of thanksgiving for the administration, and those in regional and local offices.   Depending on our partisan loyalties, this may be difficult, but perhaps we may find a blessing for ourselves in such a prayer.

What are the blessings we may miss out on when we don't have a thankful attitude?

Expressing our thanks to God.  Why can we be thankful? What do we base our thankful attitude on?  What is the benefit of an attitude of thankfulness?   How can we maintain an attitude of thankfulness? What does an attitude of gratitude empower us to do?

1) even if God didn't do anything else for us, we should be eternally grateful for our salvation through Jesus Christ (1Tim 2).

2) An attitude of thankfulness will allow us to live in harmony (peace of mind) and worry less.

3) An attitude of gratitude may set us free / empower us to become champions of God's purpose--care for the needy and poor.